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Reference

nginx objects
     HTTP Request
     Stream Session
     Periodic Session
     Headers
     Request
     Response
     ngx
     ngx.shared
built-in objects
     console
     crypto
     CryptoKey
     CryptoKeyPair
     njs
     process
     String
web API
     Text Decoder
     Text Encoder
timers
     Global functions
built-in modules
     Buffer
     Crypto
     File System
     Query String
     XML
     zlib

njs provides objects, methods and properties for extending nginx functionality.

This reference contains only njs specific properties, methods and modules not compliant with ECMAScript. Definitions of njs properties and methods compliant with ECMAScript can be found in ECMAScript specification. List of all njs properties and methods can be found in Compatibility.

nginx objects

HTTP Request

r.internalRedirect()

r.log()

r.uri

The HTTP request object is available only in the ngx_http_js_module module. Before 0.8.5, all string properties of the object were byte strings.

r.args{}

request arguments object, read-only.

The query string is returned as an object. Since 0.7.6, duplicate keys are returned as an array, keys are case-sensitive, both keys and values are percent-decoded.

For example, the query string

'a=1&b=%32&A=3&b=4&B=two%20words'

is converted to r.args as:

{a: "1", b: ["2", "4"], A: "3", B: "two words"}

More advanced parsing scenarios can be achieved with the Query String module and with the $args variable, for example:

import qs from 'querystring';

function args(r) {
    return qs.parse(r.variables.args);
}

The argument object is evaluated at the first access to r.args. If only a single argument is needed, for example foo, nginx variables can be used:

r.variables.arg_foo

Here, nginx variables object returns the first value for a given key, case-insensitive, without percent-decoding.

To convert r.args back to a string, the Query String stringify method can be used.

r.done()

after calling this function, next data chunks will be passed to client without calling js_body_filter (0.5.2). May be called only from the js_body_filter function

r.error(string)

writes a string to the error log on the error level of logging

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

r.finish()

finishes sending a response to the client

r.headersIn{}

incoming headers object, read-only.

The Foo request header can be accessed with the syntax: headersIn.foo or headersIn['Foo'].

The “Authorization”, “Content-Length”, “Content-Range”, “Content-Type”, “ETag”, “Expect”, “From”, “Host”, “If-Match”, “If-Modified-Since”, “If-None-Match”, “If-Range”, “If-Unmodified-Since”, “Max-Forwards”, “Proxy-Authorization”, “Referer”, “Transfer-Encoding”, and “User-Agent” request headers can have only one field value (0.4.1). Duplicate field values in “Cookie” headers are separated by semicolon (;). Duplicate field values in all other request headers are separated by commas.

r.headersOut{}

outgoing headers object for the main request, writable.

If r.headersOut{} is the response object of a subrequest, it represents response headers. In this case, field values in “Accept-Ranges”, “Connection”, “Content-Disposition”, “Content-Encoding”, “Content-Length”, “Content-Range”, “Date”, “Keep-Alive”, “Server”, “Transfer-Encoding”, “X-Accel-*” response headers may be omitted.

The “Foo” response header can be accessed with the syntax: headersOut.foo or headersOut['Foo'].

Outgoing headers should be set before a response header is sent to a client, otherwise header update will be ignored. This means that r.headersOut{} is effectively writable in:

the js_content handler before r.sendHeader() or r.return() are called
the js_header_filter handler

Field values of multi-value response headers (0.4.0) can be set with the syntax:

r.headersOut['Foo'] = ['a', 'b']

where the output will be:

Foo: a
Foo: b

All previous field values of the “Foo” response header will be deleted.

For standard response headers that accept only a single field value such as “Content-Type”, only the last element of the array will take effect. Field values of the “Set-Cookie” response header are always returned as an array. Duplicate field values in “Age”, “Content-Encoding”, “Content-Length”, “Content-Type”, “ETag”, “Expires”, “Last-Modified”, “Location”, “Retry-After” response headers are ignored. Duplicate field values in all other response headers are separated by commas.

r.httpVersion

HTTP version, read-only

r.internal

boolean value, true for internal locations

r.internalRedirect(uri)

performs an internal redirect to the specified uri. If the uri starts with the “@” prefix, it is considered a named location. In a new location, all request processing is repeated starting from NGX_HTTP_SERVER_REWRITE_PHASE for ordinary locations and from NGX_HTTP_REWRITE_PHASE for named locations. As a result, a redirect to a named location does not check client_max_body_size limit. See dev guide for more details. Redirected requests become internal and can access the internal locations. The actual redirect happens after the handler execution is completed.

After redirect, a new njs VM is started in the target location, the VM in the original location is stopped. Values of nginx variables are kept and can be used to pass information to the target location. Since 0.5.3, the variable declared with the js_var directive for http or stream can be used.

Since 0.7.4, the method accepts escaped URIs.

r.log(string)

writes a string to the error log on the info level of logging

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

r.method

HTTP method, read-only

r.parent

references the parent request object

r.remoteAddress

client address, read-only

r.requestBody

the property was made obsolete in 0.5.0 and was removed in 0.8.0. The r.requestBuffer or r.requestText property should be used instead.

r.requestBuffer

client request body if it has not been written to a temporary file (since 0.5.0). To ensure that the client request body is in memory, its size should be limited by client_max_body_size, and a sufficient buffer size should be set using client_body_buffer_size. The property is available only in the js_content directive.

r.requestText

the same as r.requestBuffer, but returns a string. Note that it may convert bytes invalid in UTF-8 encoding into the replacement character.

r.rawHeadersIn[]

returns an array of key-value pairs exactly as they were received from the client (0.4.1).

For example, with the following request headers:

Host: localhost
Foo:  bar
foo:  bar2

the output of r.rawHeadersIn will be:

[
    ['Host', 'localhost'],
    ['Foo', 'bar'],
    ['foo', 'bar2']
]

All foo headers can be collected with the syntax:

r.rawHeadersIn.filter(v=>v[0].toLowerCase() == 'foo').map(v=>v[1])

the output will be:

['bar', 'bar2']

Header field names are not converted to lower case, duplicate field values are not merged.

r.rawHeadersOut[]

returns an array of key-value pairs of response headers (0.4.1). Header field names are not converted to lower case, duplicate field values are not merged.

r.responseBody

the property was made obsolete in 0.5.0 and was removed in 0.8.0. The r.responseBuffer or the r.responseText property should be used instead.

r.responseBuffer

holds the subrequest response body, read-only (since 0.5.0). The size of r.responseBuffer is limited by the subrequest_output_buffer_size directive.

r.responseText

the same as r.responseBuffer but returns a string (since 0.5.0). Note that it may convert bytes invalid in UTF-8 encoding into the replacement character.

r.return(status[, string | Buffer])

sends the entire response with the specified status to the client. The response can be a string or Buffer (0.5.0).

It is possible to specify either a redirect URL (for codes 301, 302, 303, 307, and 308) or the response body text (for other codes) as the second argument

r.send(string | Buffer)

sends a part of the response body to the client. The data sent can be a string or Buffer (0.5.0)

r.sendBuffer(data[, options])

adds data to the chain of data chunks to be forwarded to the next body filter (0.5.2). The actual forwarding happens later, when the all the data chunks of the current chain are processed.

The data can be a string or Buffer. The options is an object used to override nginx buffer flags derived from an incoming data chunk buffer. The flags can be overridden with the following flags:

last: boolean, true if the buffer is the last buffer
flush: boolean, true if the buffer should have the flush flag

The method may be called only from the js_body_filter function.

r.sendHeader()

sends the HTTP headers to the client

r.setReturnValue(value)

sets the return value of the js_set handler (0.7.0). Unlike an ordinary return statement, this method should be used when the handler is JS async function. For example:

async function js_set(r) {
    const digest = await crypto.subtle.digest('SHA-256', r.headersIn.host);
    r.setReturnValue(digest);
}

r.status

status, writable

r.subrequest(uri[, options[, callback]])

creates a subrequest with the given uri and options, and installs an optional completion callback.

A subrequest shares its input headers with the client request. To send headers different from original headers to a proxied server, the proxy_set_header directive can be used. To send a completely new set of headers to a proxied server, the proxy_pass_request_headers directive can be used.

If options is a string, then it holds the subrequest arguments string. Otherwise, options is expected to be an object with the following keys:

args: arguments string, by default an empty string is used
body: request body, by default the request body of the parent request object is used
method: HTTP method, by default the GET method is used
detached: boolean flag (0.3.9), if true, the created subrequest is a detached subrequest. Responses to detached subrequests are ignored. Unlike ordinary subrequests, a detached subrequest can be created inside a variable handler. The detached flag and callback argument are mutually exclusive.

The completion callback receives a subrequest response object with methods and properties identical to the parent request object.

Since 0.3.8, if a callback is not provided, the Promise object that resolves to the subrequest response object is returned.

For example, to view all response headers in the subrequest:

async function handler(r) {
    const reply = await r.subrequest('/path');

    for (const h in reply.headersOut) {
        r.log(`${h}: ${reply.headersOut[h]}`);
    }

    r.return(200);
}

r.uri

current URI in request, normalized, read-only

r.rawVariables{}

nginx variables as Buffers, writable (since 0.5.0)

r.variables{}

nginx variables object, writable (since 0.2.8).

For example, to get the $foo variable, one of the following syntax can be used:

r.variables['foo']
r.variables.foo

Since 0.8.6, regular expression captures can be accessed using the following syntax:

r.variables['1']
r.variables[1]

nginx treats variables referenced in nginx.conf and unreferenced variables differently. When a variable is referenced, it may be cacheable, but when it is unreferenced it is always uncacheable. For example, when the $request_id variable is only accessed from njs, it has a new value every time it is evaluated. But, when the $request_id is referenced, for example:

proxy_set_header X-Request-Id $request_id;

the r.variables.request_id returns the same value every time.

A variable is writable if:

it was created using the js_var directive for http or stream (since 0.5.3)
it is referenced in nginx configuration file

Even so, some embedded variables still cannot be assigned a value (for example, $http_).

r.warn(string)

writes a string to the error log on the warning level of logging

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

Stream Session

s.log()

s.off()

s.on()

The stream session object is available only in the ngx_stream_js_module module. Before 0.8.5, all string properties of the object were byte strings.

s.allow()

an alias to s.done(0) (0.2.4)

s.decline()

an alias to s.done(-5) (0.2.4)

s.deny()

an alias to s.done(403) (0.2.4)

s.done([code])

sets an exit code for the current phase handler to a code value, by default 0. The actual finalization happens when the js handler is completed and all pending events, for example, from ngx.fetch() or setTimeout(), are processed (0.2.4).

Possible code values:

0 — successful finalization, passing control to the next phase
-5 — undecided, passing control to the next handler of the current phase (if any)
403 — access is forbidden

May be called only from a phase handler function: js_access or js_preread.

s.error(string)

writes a sent string to the error log on the error level of logging

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

s.log(string)

writes a sent string to the error log on the info level of logging

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

s.off(eventName)

unregisters the callback set by the s.on() method (0.2.4)

s.on(event, callback)

registers a callback for the specified event (0.2.4).

An event may be one of the following strings:

upload: new data (string) from a client
download: new data (string) to a client
upstream: new data (Buffer) from a client (since 0.5.0)
downstream: new data (Buffer) to a client (since 0.5.0)

The completion callback has the following prototype: callback(data, flags), where data is string or Buffer (depending on the event type) flags is an object with the following properties:

last: a boolean value, true if data is a last buffer.

s.remoteAddress

client address, read-only

s.rawVariables

nginx variables as Buffers, writable (since 0.5.0)

s.send(data[, options])

adds data to the chain of data chunks that will be forwarded in the forward direction: in download callback to a client; in upload to an upstream server (0.2.4). The actual forwarding happens later, when the all the data chunks of the current chain are processed.

The data can be a string or Buffer (0.5.0). The options is an object used to override nginx buffer flags derived from an incoming data chunk buffer. The flags can be overridden with the following flags:

last: boolean, true if the buffer is the last buffer
flush: boolean, true if the buffer should have the flush flag

The method can be called multiple times per callback invocation.

s.sendDownstream()

is identical to s.send(), except for it always sends data to a client (since 0.7.8).

s.sendUpstream()

is identical to s.send(), except for it always sends data from a client (since 0.7.8).

s.status

session status code, an alias to the $status variable, read only (since 0.5.2)

s.setReturnValue(value)

sets the return value of the js_set handler (0.7.0). Unlike an ordinary return statement, this method should be used when the handler is JS async function. For example:

async function js_set(r) {
    const digest = await crypto.subtle.digest('SHA-256', r.headersIn.host);
    r.setReturnValue(digest);
}

s.variables{}

nginx variables object, writable (since 0.2.8). A variable can be writable only if it is referenced in nginx configuration file. Even so, some embedded variables still cannot be assigned a value.

s.warn(string)

writes a sent string to the error log on the warning level of logging

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

Periodic Session

PeriodicSession.rawVariables{}

PeriodicSession.variables{}

The Periodic Session object is provided as the first argument for the js_periodic handler for http and stream (since 0.8.1).

PeriodicSession.rawVariables{}: nginx variables as Buffers, writable.
PeriodicSession.variables{}: nginx variables object, writable.

Headers

The Headers interface of the Fetch API is available since 0.5.1.

A new Headers object can be created using the Headers() constructor: (since 0.7.10):

Headers([init])

init: An object containing HTTP headers for prepopulating the Headers object, can be a string, an array of name-value pairs, or an existing Headers object.

A new Headers object can be created with the following properties and methods:

append(): Appends a new value into an existing header in the Headers object, or adds the header if it does not already exist (since 0.7.10).
delete(): Deletes a header from the Headers object (since 0.7.10).
get(): Returns a string containing the values of all headers with the specified name separated by a comma and a space.
getAll(name): Returns an array containing the values of all headers with the specified name.
forEach(): Executes a provided function once for each key/value pair in the Headers object (since 0.7.10).
has(): Returns a boolean value indicating whether a header with the specified name exists.
set(): Sets a new value for an existing header inside the Headers object, or adds the header if it does not already exist (since 0.7.10).

Request

Request()

Request.arrayBuffer()

Request.bodyUsed

Request.cache

Request.credentials

The Request interface of the Fetch API is available since 0.7.10.

A new Request object can be created using the Request() constructor:

Request[resource[, options]])

Creates a Request object to fetch that can be passed later to ngx.fetch(). The resource can be a URL or an existing Request object. The options is an optional argument that is expected to be an object with the following keys:

body: The request body, by default is empty.
headers: The response headers object — the object containing HTTP headers for prepopulating the Headers object, can be a string, an array of name-value pairs, or an existing Headers object.
method: The HTTP method, by default the GET method is used.

A new Request object can be created with the following properties and methods:

arrayBuffer(): Returns a Promise that resolves with an ArrayBuffer.
bodyUsed: A boolean value, true if the body was used in the request.
cache: Contains the cache mode of the request.
credentials: Contains the credentials of the request, by default is same-origin.
headers: The Headers read-only object associated with the Request.
json(): Returns a Promise that resolves with the result of parsing the request body as JSON.
method: Contains the request method.
mode: Contains the mode of the request.
text(): Returns a Promise that resolves with a string representation of the request body.
url: Contains the URL of the request.

Response

Response()

Response.arrayBuffer()

Response.redirected

Response.status

Response.statusText

Response.text()

Response.type

Response.url

The Response interface is available since 0.5.1.

A new Response object can be created using the Response() constructor (since 0.7.10):

Response[body[, options]])

Creates a Response object. The body is an optional argument, can be a string or a buffer, by default is null. The options is an optional argument that is expected to be an object with the following keys:

headers: The response headers object — the object containing HTTP headers for prepopulating the Headers object, can be a string, an array of name-value pairs, or an existing Headers object.
status: The status code of the response.
statusText: The status message corresponding to the status code.

A new Response() object can be created with the following properties and methods:

arrayBuffer(): Takes a Response stream and reads it to completion. Returns a Promise that resolves with an ArrayBuffer.
bodyUsed: A boolean value, true if the body was read.
headers: The Headers read-only object associated with the Response.
json(): Takes a Response stream and reads it to completion. Returns a Promise that resolves with the result of parsing the body text as JSON.
ok: A boolean value, true if the response was successful (status codes between 200–299).
redirected: A boolean value, true if the response is the result of a redirect.
status: The status code of the response.
statusText: The status message corresponding to the status code.
text(): Takes a Response stream and reads it to completion. Returns a Promise that resolves with a string.
type: The type of the response.
url: The URL of the response.

ngx

The ngx global object is available since 0.5.0.

ngx.build

a string containing an optional nginx build name, corresponds to the --build=name argument of the configure script, by default is "" (0.8.0)

ngx.conf_file_path

a string containing the file path to current nginx configuration file (0.8.0)

ngx.conf_prefix

a string containing the file path to nginx configuration prefix — the directory where nginx is currently looking for configuration (0.7.8)

ngx.error_log_path

a string containing the file path to the current error log file (0.8.0)

ngx.fetch(resource, [options])

Makes a request to fetch a resource (0.5.1), which can be an URL or the Request object (0.7.10). Returns a Promise that resolves with the Response object. Since 0.7.0, the https:// scheme is supported, redirects are not handled.

If the URL in the resource is specified as a domain name, it is determined using a resolver. If the https:// scheme is specified, the js_fetch_trusted_certificate directive should be configured for the authentication of the resource's HTTPS server.

The options parameter is expected to be an object with the following keys:

body: request body, by default is empty
buffer_size: the buffer size for reading the response, by default is 4096
headers: request headers object
max_response_body_size: the maximum size of the response body in bytes, by default is 32768
method: HTTP method, by default the GET method is used
verify: enables or disables verification of the HTTPS server certificate, by default is true (0.7.0)

Example:

let reply = await ngx.fetch('http://nginx.org/');
let body = await reply.text();

r.return(200, body);

ngx.log(level, message)

writes a message to the error log with the specified level of logging. The level parameter specifies one of the log levels, the message parameter can be a string or Buffer. The following log levels can be specified: ngx.INFO, ngx.WARN, and ngx.ERR.

As nginx has a hardcoded maximum line length limit, only first 2048 bytes of the string can be logged.

ngx.prefix

a string containing the file path to nginx prefix — a directory that keeps server files (0.8.0)

ngx.version

a string containing nginx version, for example: 1.25.0 (0.8.0)

ngx.version_number

a number containing nginx version, for example: 1025000 (0.8.0)

ngx.worker_id

a number that corresponds to nginx internal worker id, the value is between 0 and the value specified in the worker_processes directive (0.8.0)

ngx.shared

The ngx.shared global object is available since 0.8.0.

SharedDict

ngx.shared.SharedDict.add()

ngx.shared.SharedDict.capacity

ngx.shared.SharedDict.clear()

ngx.shared.SharedDict.delete()

ngx.shared.SharedDict.freeSpace()

ngx.shared.SharedDict.get()

ngx.shared.SharedDict.has()

ngx.shared.SharedDict.incr()

ngx.shared.SharedDict.items()

ngx.shared.SharedDict.keys()

ngx.shared.SharedDict.name

ngx.shared.SharedDict.pop()

ngx.shared.SharedDict.replace()

ngx.shared.SharedDict.set()

ngx.shared.SharedDict.size()

ngx.shared.SharedDict.type

The shared dictionary object is available since 0.8.0. The shared dictionary name, type, and size are set with the js_shared_dict_zone directive in http or stream.

A SharedDict() object has the following properties and methods:

ngx.shared.SharedDict.add(key, value [,timeout])

Sets the value for the specified key in the dictionary only if the key does not exist yet. The key is a string representing the key of the item to add, the value is the value of the item to add.

The optional timeout argument is specified in milliseconds and overrides the timeout parameter of the js_shared_dict_zone directive in http or stream (since 0.8.5). It can be useful when some keys are expected to have unique timeouts.

Returns true if the value has been successfully added to the SharedDict dictionary, false if the key already exists in the dictionary. Throws SharedMemoryError if there is not enough free space in the SharedDict dictionary. Throws TypeError if the value is of a different type than expected by this dictionary.

ngx.shared.SharedDict.capacity

Returns the capacity of the SharedDict dictionary, corresponds to the size parameter of js_shared_dict_zone directive in http or stream.

ngx.shared.SharedDict.clear()

Removes all items from the SharedDict dictionary.

ngx.shared.SharedDict.delete(key)

Removes the item associated with the specified key from the SharedDict dictionary, true if the item in the dictionary existed and was removed, false otherwise.

ngx.shared.SharedDict.freeSpace()

Returns the free page size in bytes. If the size is zero, the SharedDict dictionary will still accept new values if there is space in the occupied pages.

ngx.shared.SharedDict.get(key)

Retrieves the item by its key, returns the value associated with the key or undefined if there is none.

ngx.shared.SharedDict.has(key)

Searches for an item by its key, returns true if such item exists or false otherwise.

ngx.shared.SharedDict.incr(key,delta[[,init], timeout]))

Increments the integer value associated with the key by delta. The key is a string, the delta is the number to increment or decrement the value by. If the key does not exist, the item will be initialized to an optional init argument, by default is 0.

Returns the new value. Throws SharedMemoryError if there is not enough free space in the SharedDict dictionary. Throws TypeError if this dictionary does not expect numbers.

This method can be used only if the dictionary type was declared with type=number parameter of the js_shared_dict_zone directive in http or stream.

ngx.shared.SharedDict.items([maxCount])

Returns an array of the SharedDict dictionary key-value items (since 0.8.1). The maxCount parameter sets maximum number of items to retrieve, by default is 1024.

ngx.shared.SharedDict.keys([maxCount])

Returns an array of the SharedDict dictionary keys. The maxCount parameter sets maximum number of keys to retrieve, by default is 1024.

ngx.shared.SharedDict.name

Returns the name of the SharedDict dictionary, corresponds to the zone= parameter of js_shared_dict_zone directive in http or stream.

ngx.shared.SharedDict.pop(key)

Removes the item associated with the specified key from the SharedDict dictionary, returns the value associated with the key or undefined if there is none.

ngx.shared.SharedDict.replace(key, value)

Replaces the value for the specified key only if the key already exists, returns true if the value was successfully replaced, false if the key does not exist in the SharedDict dictionary. Throws SharedMemoryError if there is not enough free space in the SharedDict dictionary. Throws TypeError if the value is of a different type than expected by this dictionary.

ngx.shared.SharedDict.set(key, value [,timeout])

Sets the value for the specified key, returns this SharedDict dictionary (for method chaining).

ngx.shared.SharedDict.size()

Returns the number of items for the SharedDict dictionary.

ngx.shared.SharedDict.type

Returns string or number that corresponds to the SharedDict dictionary type set by the type= parameter of js_shared_dict_zone directive in http or stream.

built-in objects

console

The console object is available in nginx since 0.8.2, in CLI since 0.2.6.

console.error(msg[, msg2 ...]): Outputs one or more error messages. The message may be a string or an object.
console.info(msg[, msg2 ...]): Outputs one or more info messages. The message may be a string or an object.
console.log(msg[, msg2 ...]): Outputs one or more log messages. The message may be a string or an object.
console.time(label): Starts a timer that can track how long an operation takes. The label parameter allows naming different timers. If console.timeEnd() with the same name is called, the time that elapsed since the timer was started will be output, in milliseconds.
console.timeEnd(label): Stops a timer previously started by console.time() The label parameter allows naming different timers.
console.warn(msg[, msg2 ...]): Outputs one or more warning messages. The message may be a string or an object.

crypto

сrypto.getRandomValues()

сrypto.subtle.encrypt()

сrypto.subtle.decrypt()

сrypto.subtle.deriveBits()

сrypto.subtle.deriveKey()

сrypto.subtle.digest()

сrypto.subtle.exportKey()

сrypto.subtle.generateKey()

сrypto.subtle.importKey()

сrypto.subtle.sign()

сrypto.subtle.verify()

The crypto object is a global object that allows using cryptographic functionality (since 0.7.0).

сrypto.getRandomValues(typedArray)

Gets cryptographically strong random values. Returns the same array passed as typedArray but with its contents replaced with the newly generated random numbers. Possible values:

typedArray: can be Int8Array, Int16Array, Uint16Array, Int32Array, or Uint32Array

сrypto.subtle.encrypt(algorithm, key, data)

Encrypts data using the provided algorithm and key. Returns a Promise that fulfills with an ArrayBuffer containing the ciphertext. Possible values:

algorithm

an object that specifies the algorithm to be used and any extra parameters if required:

for RSA-OAEP, pass the object with the following keys:
- name is a string, should be set to RSA-OAEP:
```
crypto.subtle.encrypt({name: "RSA-OAEP"}, key, data)
```
for AES-CTR, pass the object with the following keys:
- name is a string, should be set to AES-CTR
- counter is an ArrayBuffer, TypedArray, or DataView — the initial value of the counter block, must be 16 bytes long (the AES block size). The rightmost length bits of this block are used for the counter, and the rest is used for the nonce. For example, if length is set to 64, then the first half of counter is the nonce and the second half is used for the counter
- length is the number of bits in the counter block that are used for the actual counter. The counter must be big enough that it doesn't wrap.
for AES-CBC, pass the object with the following keys:
- name is a string, should be set to AES-CBC
- iv or the initialization vector, is an ArrayBuffer, TypedArray, or DataView, must be 16 bytes, unpredictable, and preferably cryptographically random. However, it need not be secret, for example, it may be transmitted unencrypted along with the ciphertext.
for AES-GCM, pass the object with the following keys:
- name is a string, should be set to AES-GCM
- iv or the initialization vector, is an ArrayBuffer, TypedArray, or DataView, must be 16 bytes, and must be unique for every encryption operation carried out with a given key
- additionalData (optional) is an ArrayBuffer, TypedArray, or DataView that contains additional data that will not be encrypted but will be authenticated along with the encrypted data. If additionalData is specified, then the same data must be specified in the corresponding call to decrypt(): if the data given to the decrypt() call does not match the original data, the decryption will throw an exception. The bit length of additionalData must be smaller than 2^64 - 1.
- tagLength (optional, default is 128) - a number that determines the size in bits of the authentication tag generated in the encryption operation and used for authentication in the corresponding decryption Possible values: 32, 64, 96, 104, 112, 120, or 128. The AES-GCM specification recommends that it should be 96, 104, 112, 120, or 128, although 32 or 64 bits may be acceptable in some applications.

key

a CryptoKey that contains the key to be used for encryption

data

an ArrayBuffer, TypedArray, or DataView that contains the data to be encrypted (also known as the plaintext)

сrypto.subtle.decrypt(algorithm, key, data)

Decrypts encrypted data. Returns a Promise with the decrypted data. Possible values:

algorithm

an object that specifies the algorithm to be used, and any extra parameters as required. The values given for the extra parameters must match those passed into the corresponding encrypt() call.

for RSA-OAEP, pass the object with the following keys:
- name is a string, should be set to RSA-OAEP:
```
crypto.subtle.encrypt({name: "RSA-OAEP"}, key, data)
```
for AES-CTR, pass the object with the following keys:
- name is a string, should be set to AES-CTR
- counter is an ArrayBuffer, TypedArray, or DataView — the initial value of the counter block, must be 16 bytes long (the AES block size). The rightmost length bits of this block are used for the counter, and the rest is used for the nonce. For example, if length is set to 64, then the first half of counter is the nonce and the second half is used for the counter.
- length is the number of bits in the counter block that are used for the actual counter. The counter must be big enough that it doesn't wrap.
for AES-CBC, pass the object with the following keys:
- name is a string, should be set to AES-CBC
- iv or the initialization vector, is an ArrayBuffer, TypedArray, or DataView, must be 16 bytes, unpredictable, and preferably cryptographically random. However, it need not be secret (for example, it may be transmitted unencrypted along with the ciphertext).
for AES-GCM, pass the object with the following keys:
- name is a string, should be set to AES-GCM
- iv or the initialization vector, is an ArrayBuffer, TypedArray, or DataView, must be 16 bytes, and must be unique for every encryption operation carried out with a given key
- additionalData (optional) is an ArrayBuffer, TypedArray, or DataView that contains additional data that will not be encrypted but will be authenticated along with the encrypted data. If additionalData is specified, then the same data must be specified in the corresponding call to decrypt(): if the data given to the decrypt() call does not match the original data, the decryption will throw an exception. The bit length of additionalData must be smaller than 2^64 - 1.
- tagLength (optional, default is 128) - a number that determines the size in bits of the authentication tag generated in the encryption operation and used for authentication in the corresponding decryption. Possible values: 32, 64, 96, 104, 112, 120, or 128. The AES-GCM specification recommends that it should be 96, 104, 112, 120, or 128, although 32 or 64 bits may be acceptable in some applications.

key

a CryptoKey that contains the key to be used for decryption. If RSA-OAEP is used, this is the privateKey property of the CryptoKeyPair object.

data

an ArrayBuffer, TypedArray, or DataView that contains the data to be decrypted (also known as ciphertext)

сrypto.subtle.deriveBits(algorithm, baseKey, length)

Derives an array of bits from a base key. Returns a Promise which will be fulfilled with an ArrayBuffer that contains the derived bits. Possible values:

algorithm

is an object that defines the derivation algorithm to use:

for HKDF, pass the object with the following keys:
- name is a string, should be set to HKDF
- hash is a string with the digest algorithm to use: SHA-1, SHA-256, SHA-384, or SHA-512
- salt is an ArrayBuffer, TypedArray, or DataView that represents random or pseudo-random value with the same length as the output of the digest function. Unlike the input key material passed into deriveKey(), salt does not need to be kept secret.
- info is an ArrayBuffer, TypedArray, or DataView that represents application-specific contextual information used to bind the derived key to an application or context, and enables deriving different keys for different contexts while using the same input key material. This property is required but may be an empty buffer.
for PBKDF2, pass the object with the following keys:
- name is a string, should be set to PBKDF2
- hash is a string with the digest algorithm to use: SHA-1, SHA-256, SHA-384, or SHA-512
- salt is an ArrayBuffer, TypedArray, or DataView that represents random or pseudo-random value of at least 16 bytes. Unlike the input key material passed into deriveKey(), salt does not need to be kept secret.
- iterations is a number that represents the number of times the hash function will be executed in deriveKey()

baseKey

is a CryptoKey that represents the input to the derivation algorithm - the initial key material for the derivation function: for example, for PBKDF2 it might be a password, imported as a CryptoKey using сrypto.subtle.importKey()

length

is a number representing the number of bits to derive. For browsers compatibility, the number should be a multiple of 8

сrypto.subtle.deriveKey(algorithm, baseKey, derivedKeyAlgorithm, extractable, keyUsages)

Derives a secret key from a master key. Possible values:

algorithm

is an object that defines the derivation algorithm to use:

for HKDF, pass the object with the following keys:
- name is a string, should be set to HKDF
- hash is a string with the digest algorithm to use: SHA-1, SHA-256, SHA-384, or SHA-512
- salt is an ArrayBuffer, TypedArray, or DataView that represents random or pseudo-random value with the same length as the output of the digest function. Unlike the input key material passed into deriveKey(), salt does not need to be kept secret.
- info is an ArrayBuffer, TypedArray, or DataView that represents application-specific contextual information used to bind the derived key to an application or context, and enables deriving different keys for different contexts while using the same input key material. This property is required but may be an empty buffer.
for PBKDF2, pass the object with the following keys:
- name is a string, should be set to PBKDF2
- hash is a string with the digest algorithm to use: SHA-1, SHA-256, SHA-384, or SHA-512
- salt is an ArrayBuffer, TypedArray, or DataView that represents random or pseudo-random value of at least 16 bytes. Unlike the input key material passed into deriveKey(), salt does not need to be kept secret.
- iterations is a number that represents the number of times the hash function will be executed in deriveKey()

baseKey

derivedKeyAlgorithm

is an object that defines the algorithm the derived key will be used for:

for HMAC, pass the object with the following keys:
- name is a string, should be set to HMAC
- hash is a string with the name of the digest function to use: SHA-1, SHA-256, SHA-384, or SHA-512
- length (optional) is a number that represents the length in bits of the key. If not specified, the length of the key is equal to the block size of the chozen hash function
for AES-CTR, AES-CBC, or AES-GCM, pass the object with the following keys:
- name is a string, should be set to AES-CTR, AES-CBC, or AES-GCM, depending on the algorithm used
- length is a number that represents the length in bits of the key to generate: 128, 192, or 256

extractable

is a boolean value that indicates whether it will be possible to export the key

keyUsages

is an Array that indicates what can be done with the derived key. The key usages must be allowed by the algorithm set in derivedKeyAlgorithm. Possible values:

encrypt: key for encrypting messages
decrypt: key for decrypting messages
sign: key for signing messages
verify: key for verifying signatures
deriveKey: key for deriving a new key
deriveBits: key for deriving bits
wrapKey: key for wrapping a key
unwrapKey: key for unwrapping a key

сrypto.subtle.digest(algorithm, data)

Generates a digest of the given data. Takes as its arguments an identifier for the digest algorithm to use and the data to digest. Returns a Promise which will be fulfilled with the digest. Possible values:

algorithm: is a string that defines the hash function to use: SHA-1 (not for cryptographic applications), SHA-256, SHA-384, or SHA-512
data: is an ArrayBuffer, TypedArray, or DataView that contains the data to be digested

сrypto.subtle.exportKey(format, key)

Exports a key: takes a key as a CryptoKey object and returns the key in an external, portable format (since 0.7.10). If the format was jwk, then the Promise fulfills with a JSON object containing the key. Otherwise, the promise fulfills with an ArrayBuffer containing the key. Possible values:

format

a string that describes the data format in which the key should be exported, can be the following:

raw: the raw data format
pkcs8: the PKCS #8 format
spki: the SubjectPublicKeyInfo format
jwk: the JSON Web Key (JWK) format (since 0.7.10)

key

the CryptoKey that contains the key to be exported

сrypto.subtle.generateKey(algorithm, extractable, usage)

Generates a new key for symmetric algorithms or key pair for public-key algorithms (since 0.7.10). Returns a Promise that fulfills with the generated key as a CryptoKey or CryptoKeyPair object. Possible values:

algorithm

a dictionary object that defines the type of key to generate and provides extra algorithm-specific parameters:

for RSASSA-PKCS1-v1_5, RSA-PSS, or RSA-OAEP, pass the object with the following keys:
- name is a string, should be set to RSASSA-PKCS1-v1_5, RSA-PSS, or RSA-OAEP, depending on the used algorithm
- hash is a string that represents the name of the digest function to use, can be SHA-256, SHA-384, or SHA-512
for ECDSA, pass the object with the following keys:
- name is a string, should be set to ECDSA
- namedCurve is a string that represents the name of the elliptic curve to use, may be P-256, P-384, or P-521
for HMAC, pass the object with the following keys:
- name is a string, should be set to HMAC
- hash is a string that represents the name of the digest function to use, can be SHA-256, SHA-384, or SHA-512
- length (optional) is a number that represents the length in bits of the key. If omitted, the length of the key is equal to the length of the digest generated by the chosen digest function.
for AES-CTR, AES-CBC, or AES-GCM, pass the string identifying the algorithm or an object of the form { "name": "ALGORITHM" }, where ALGORITHM is the name of the algorithm

extractable

boolean value that indicates if it is possible to export the key

usage

an array that indicates possible actions with the key:

encrypt: key for encrypting messages
decrypt: key for decrypting messages
sign: key for signing messages
verify: key for verifying signatures
deriveKey: key for deriving a new key
deriveBits: key for deriving bits
wrapKey: key for wrapping a key
unwrapKey: key for unwrapping a key

сrypto.subtle.importKey(format, keyData, algorithm, extractable, keyUsages)

Imports a key: takes as input a key in an external, portable format and gives a CryptoKey object. Returns a Promise that fulfills with the imported key as a CryptoKey object. Possible values:

format

a string that describes the data format of the key to import, can be the following:

raw: the raw data format
pkcs8: the PKCS #8 format
spki: the SubjectPublicKeyInfo format
jwk: the JSON Web Key (JWK) format (since 0.7.10)

keyData

the ArrayBuffer, TypedArray, or DataView object that contains the key in the given format

algorithm

a dictionary object that defines the type of key to import and provides extra algorithm-specific parameters:

for RSASSA-PKCS1-v1_5, RSA-PSS, or RSA-OAEP, pass the object with the following keys:
- name is a string, should be set to RSASSA-PKCS1-v1_5, RSA-PSS, or RSA-OAEP, depending on the used algorithm
- hash is a string that represents the name of the digest function to use, can be SHA-1, SHA-256, SHA-384, or SHA-512
for ECDSA, pass the object with the following keys:
- name is a string, should be set to ECDSA
- namedCurve is a string that represents the name of the elliptic curve to use, may be P-256, P-384, or P-521
for HMAC, pass the object with the following keys:
- name is a string, should be set to HMAC
- hash is a string that represents the name of the digest function to use, can be SHA-256, SHA-384, or SHA-512
- length (optional) is a number that represents the length in bits of the key. If omitted, the length of the key is equal to the length of the digest generated by the chosen digest function.
for AES-CTR, AES-CBC, or AES-GCM, pass the string identifying the algorithm or an object of the form { "name": "ALGORITHM" }, where ALGORITHM is the name of the algorithm
for PBKDF2, pass the PBKDF2 string
for HKDF, pass the HKDF string

extractable

boolean value that indicates if it is possible to export the key

keyUsages

an array that indicates possible actions with the key:

encrypt: key for encrypting messages
decrypt: key for decrypting messages
sign: key for signing messages
verify: key for verifying signatures
deriveKey: key for deriving a new key
deriveBits: key for deriving bits
wrapKey: key for wrapping a key
unwrapKey: key for unwrapping a key

сrypto.subtle.sign(algorithm, key, data)

Returns signature as a Promise that fulfills with an ArrayBuffer containing the signature. Possible values:

algorithm

is a string or object that specifies the signature algorithm to use and its parameters:

for RSASSA-PKCS1-v1_5, pass the string identifying the algorithm or an object of the form { "name": "ALGORITHM" }
for RSA-PSS, pass the object with the following keys:
- name is a string, should be set to RSA-PSS
- saltLength is a long integer that represents the length of the random salt to use, in bytes
for ECDSA, pass the object with the following keys:
- name is a string, should be set to ECDSA
- hash is an identifier for the digest algorithm to use, can be SHA-256, SHA-384, or SHA-512
for HMAC, pass the string identifying the algorithm or an object of the form { "name": "ALGORITHM" }

key

is a CryptoKey object that the key to be used for signing. If algorithm identifies a public-key cryptosystem, this is the private key.

data

is an ArrayBuffer, TypedArray, or DataView object that contains the data to be signed

сrypto.subtle.verify(algorithm, key, signature, data)

Verifies a digital signature, returns a Promise that fulfills with a boolean value: true if the signature is valid, otherwise false. Possible values:

algorithm

is a string or object that specifies the algorithm to use and its parameters:

for RSASSA-PKCS1-v1_5, pass the string identifying the algorithm or an object of the form { "name": "ALGORITHM" }
for RSA-PSS, pass the object with the following keys:
- name is a string, should be set to RSA-PSS
- saltLength is a long integer that represents the length of the random salt to use, in bytes
for ECDSA, pass the object with the following keys:
- name is a string, should be set to ECDSA
- hash is an identifier for the digest algorithm to use, can be SHA-256, SHA-384, or SHA-512
for HMAC, pass the string identifying the algorithm or an object of the form { "name": "ALGORITHM" }

key

is a CryptoKey object that the key to be used for verifying. It is the secret key for a symmetric algorithm and the public key for a public-key system.

signature

is an ArrayBuffer, TypedArray, or DataView that contains the signature to verify

data

is an ArrayBuffer, TypedArray, or DataView object that contains the data whose signature is to be verified

CryptoKey

CryptoKey.algorithm

CryptoKey.extractable

CryptoKey.type

CryptoKey.usages

The CryptoKey object represents a cryptographic key obtained from one of the SubtleCrypto methods: сrypto.subtle.generateKey(), сrypto.subtle.deriveKey(), сrypto.subtle.importKey().

CryptoKey.algorithm

returns an object describing the algorithm for which this key can be used and any associated extra parameters (since 0.8.0), read-only

CryptoKey.extractable

a boolean value, true if the key can be exported (since 0.8.0), read-only

CryptoKey.type

a string value that indicates which kind of key is represented by the object, read-only. Possible values:

secret: This key is a secret key for use with a symmetric algorithm.
private: This key is the private half of an asymmetric algorithm's CryptoKeyPair
public: This key is the public half of an asymmetric algorithm's CryptoKeyPair.

CryptoKey.usages

An array of strings indicating what this key can be used for (since 0.8.0), read-only. Possible array values:

encrypt: key for encrypting messages
decrypt: key for decrypting messages
sign: key for signing messages
verify: key for verifying signatures
deriveKey: key for deriving a new key
deriveBits: key for deriving bits

CryptoKeyPair

CryptoKeyPair.privateKey

CryptoKeyPair.publicKey

The CryptoKeyPair is a dictionary object of the WebCrypto API that represents an asymmetric key pair.

CryptoKeyPair.privateKey: A CryptoKey object representing the private key.
CryptoKeyPair.publicKey: A CryptoKey object representing the public key.

njs

The njs object is a global object that represents the current VM instance (since 0.2.0).

njs.version

Returns a string with the current version of njs (for example, “0.7.4”).

njs.version_number

Returns a number with the current version of njs. For example, “0.7.4” is returned as 0x000704 (since 0.7.4).

njs.dump(value)

Returns the pretty-print string representation for a value.

njs.memoryStats

Object containing memory statistics for current VM instance (since 0.7.8).

size: amount of memory in bytes njs memory pool claimed from the operating system.

njs.on(event, callback)

Registers a callback for the specified VM event (since 0.5.2). An event may be one of the following strings:

exit: is called before the VM is destroyed. The callback is called without arguments.

process

The process object is a global object that provides information about the current process (0.3.3).

process.argv: Returns an array that contains the command line arguments passed when the current process was launched.
process.env: Returns an object containing the user environment.
By default, nginx removes all environment variables inherited from its parent process except the TZ variable. Use the env directive to preserve some of the inherited variables.
process.kill(pid, number | string): Sends the signal to the process identified by pid. Signal names are numbers or strings such as 'SIGINT' or 'SIGHUP'. See kill(2) for more information.
process.pid: Returns the PID of the current process.
process.ppid: Returns the PID of the current parent process.

String

By default all strings in njs are Unicode strings. They correspond to ECMAScript strings that contain Unicode characters. Before 0.8.0, byte strings were also supported.

Byte strings

Since 0.8.0, the support for byte strings and byte string methods were removed. When working with byte sequence, the Buffer object and Buffer properties, such as r.requestBuffer, r.rawVariables, should be used.

Byte strings contain a sequence of bytes and are used to serialize Unicode strings to external data and deserialize from external sources. For example, the toUTF8() method serializes a Unicode string to a byte string using UTF-8 encoding:

>> '£'.toUTF8().toString('hex')
'c2a3'  /* C2 A3 is the UTF-8 representation of 00A3 ('£') code point */

The toBytes() method serializes a Unicode string with code points up to 255 into a byte string, otherwise, null is returned:

>> '£'.toBytes().toString('hex')
'a3'  /* a3 is a byte equal to 00A3 ('£') code point  */

String.bytesFrom(array | string, encoding)

The method was made obsolete in 0.4.4 and was removed in 0.8.0. The Buffer.from method should be used instead:

>> Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]).toString()
'buffer'

>> Buffer.from('YnVmZmVy', 'base64').toString()
'buffer'

Before 0.4.4, created a byte string either from an array that contained octets, or from an encoded string (0.2.3), the encoding could be hex, base64, and base64url.

String.prototype.fromBytes(start[, end])

the property was made obsolete in 0.7.7 and was removed in 0.8.0. Before 0.7.7, returned a new Unicode string from a byte string where each byte was replaced with a corresponding Unicode code point.

String.prototype.fromUTF8(start[, end])

the property was made obsolete in 0.7.7 and was removed in 0.8.0. The TextDecoder method should be used instead. Before 0.7.7, converted a byte string containing a valid UTF-8 string into a Unicode string, otherwise null was returned.

String.prototype.toBytes(start[, end])

the property was made obsolete in 0.7.7 and was removed in 0.8.0. Before 0.7.7, serialized a Unicode string to a byte string, returned null if a character larger than 255 was found in the string.

String.prototype.toString(encoding)

the property was made obsolete in 0.7.7 and was removed in 0.8.0. Before 0.7.7, encoded a string to hex, base64, or base64url:

>>  'αβγδ'.toString('base64url')
'zrHOss6zzrQ'

Before version 0.4.3, only a byte string could be encoded:

>>  'αβγδ'.toUTF8().toString('base64url')
'zrHOss6zzrQ'

String.prototype.toUTF8(start[, end])

the property was made obsolete in 0.7.7 and was removed in 0.8.0. The TextEncoder method should be used instead. Before 0.7.7, serialized a Unicode string to a byte string using UTF-8 encoding:

>> 'αβγδ'.toUTF8().length
8
>> 'αβγδ'.length
4

web API

Text Decoder

TextDecoder()

TextDecoder.prototype.encoding

TextDecoder.prototype.fatal

TextDecoder.prototype.ignoreBOM

TextDecoder.prototype.decode()

The TextDecoder produces a stream of code points from a stream of bytes (0.4.3).

TextDecoder([[encoding], options])

Creates a new TextDecoder object for specified encoding, currently, only UTF-8 is supported. The options is TextDecoderOptions dictionary with the property:

fatal: boolean flag indicating if TextDecoder.decode() must throw the TypeError exception when a coding error is found, by default is false.

TextDecoder.prototype.encoding

Returns a string with the name of the encoding used by TextDecoder(), read-only.

TextDecoder.prototype.fatal

boolean flag, true if the error mode is fatal, read-only.

TextDecoder.prototype.ignoreBOM

boolean flag, true if the byte order marker is ignored, read-only.

TextDecoder.prototype.decode(buffer, [options])

Returns a string with the text decoded from the buffer by TextDecoder(). The buffer can be ArrayBuffer. The options is TextDecodeOptions dictionary with the property:

stream: boolean flag indicating if additional data will follow in subsequent calls to decode(): true if processing the data in chunks, and false for the final chunk or if the data is not chunked. By default is false.

>> (new TextDecoder()).decode(new Uint8Array([206,177,206,178]))
αβ

Text Encoder

TextEncoder()

TextEncoder.prototype.encode()

TextEncoder.prototype.encodeInto()

The TextEncoder object produces a byte stream with UTF-8 encoding from a stream of code points (0.4.3).

TextEncoder()

Returns a newly constructed TextEncoder that will generate a byte stream with UTF-8 encoding.

TextEncoder.prototype.encode(string)

Encodes string into a Uint8Array with UTF-8 encoded text.

TextEncoder.prototype.encodeInto(string, uint8Array)

Encodes a string to UTF-8, puts the result into destination Uint8Array, and returns a dictionary object that shows the progress of the encoding. The dictionary object contains two members:

read: the number of UTF-16 units of code from the source string converted to UTF-8
written: the number of bytes modified in the destination Uint8Array

timers

clearTimeout()

setTimeout()

clearTimeout(timeout)

Cancels a timeout object created by setTimeout().

setTimeout(function, milliseconds[, argument1, argumentN])

Calls a function after a specified number of milliseconds. One or more optional arguments can be passed to the specified function. Returns a timeout object.

function handler(v)
{
    // ...
}

t = setTimeout(handler, 12);

// ...

clearTimeout(t);

Global functions

atob()

btoa()

atob(encodedData)

Decodes a string of data which has been encoded using Base64 encoding. The encodedData parameter is a binary string that contains Base64-encoded data. Returns a string that contains decoded data from encodedData.

The similar btoa() method can be used to encode and transmit data which may otherwise cause communication problems, then transmit it and use the atob() method to decode the data again. For example, you can encode, transmit, and decode control characters such as ASCII values 0 through 31.

const encodedData = btoa("text to encode"); // encode a string
const decodedData = atob(encodedData); // decode the string

btoa(stringToEncode)

Creates a Base64-encoded ASCII string from a binary string. The stringToEncode parameter is a binary string to encode. Returns an ASCII string containing the Base64 representation of stringToEncode.

The method can be used to encode data which may otherwise cause communication problems, transmit it, then use the atob() method to decode the data again. For example, you can encode control characters such as ASCII values 0 through 31.

const encodedData = btoa("text to encode"); // encode a string
const decodedData = atob(encodedData); // decode the string

built-in modules

Buffer

Buffer.alloc()

Buffer.allocUnsafe()

Buffer.byteLength()

Buffer.compare()

Buffer.concat()

Buffer.from(array)

Buffer.from(arrayBuffer)

Buffer.from(buffer)

Buffer.from(object)

Buffer.from(string)

Buffer.isBuffer()

Buffer.isEncoding()

buf.writeDoubleBE()

buf.writeDoubleLE()

buf.writeFloatBE()

buf.writeFloatLE()

Buffer.alloc(size[, fill[, encoding]]))

Allocates a new Buffer of a specified size. If fill is not specified, the Buffer will be zero-filled. If fill is specified, the allocated Buffer will be initialized by calling buf.fill(fill). If fill and encoding are specified, the allocated Buffer will be initialized by calling buf.fill(fill, encoding).

The fill parameter may be a string, Buffer, Uint8Array, or integer.

Buffer.allocUnsafe(size)

The same as Buffer.alloc(), with the difference that the memory allocated for the buffer is not initialized, the contents of the new buffer is unknown and may contain sensitive data.

Buffer.byteLength(value[, encoding])

Returns the byte length of a specified value, when encoded using encoding. The value can be a string, Buffer, TypedArray, DataView, or ArrayBuffer. If the value is a string, the encoding parameter is its encoding, can be utf8, hex, base64, base64url; by default is utf8.

Buffer.compare(buffer1, buffer2)

Compares buffer1 with buffer2 when sorting arrays of Buffer instances. Returns 0 if buffer1 is the same as buffer2, 1 if buffer2 should come before buffer1 when sorted, or -1 if buffer2 should come after buffer1 when sorted.

Buffer.concat(list[, totalLength])

Returns a new Buffer which is the result of concatenating all the Buffer instances in the list. If there are no items in the list or the total length is 0, a new zero-length Buffer is returned. If totalLength is not specified, it is calculated from the Buffer instances in list by adding their lengths. If totalLength is specified, it is coerced to an unsigned integer. If the combined length of the Buffers in list exceeds totalLength, the result is truncated to totalLength.

Buffer.from(array)

Allocates a new Buffer using an array of bytes in the range 0 – 255. Array entries outside that range will be truncated.

Buffer.from(arrayBuffer, byteOffset[, length]])

Creates a view of the ArrayBuffer without copying the underlying memory. The optional byteOffset and length arguments specify a memory range within the arrayBuffer that will be shared by the Buffer.

Buffer.from(buffer)

Copies the passed buffer data onto a new Buffer instance.

Buffer.from(object[, offsetOrEncoding[, length]])

For objects whose valueOf() function returns a value not strictly equal to object, returns Buffer.from(object.valueOf(), offsetOrEncoding, length).

Buffer.from(string[, encoding])

Creates a new Buffer with a string. The encoding parameter identifies the character encoding to be used when converting a string into bytes. The encoding can be utf8, hex, base64, base64url; by default is utf8.

Buffer.isBuffer(object)

A boolean value, returns true if object is a Buffer.

Buffer.isEncoding(encoding)

A boolean value, returns true if encoding is the name of a supported character encoding.

buffer[index]

The index operator that can be used to get and set the octet at position index in buffer. The values refer to individual bytes, so the legal value range is between 0 and 255 (decimal).

buf.buffer

The underlying ArrayBuffer object based on which this Buffer object is created.

buf.byteOffset

An integer, specifying the byteOffset of the Buffers underlying ArrayBuffer object.

buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])

Compares buffer with target and returns a number indicating whether buffer comes before, after, or is the same as target in sort order. Comparison is based on the actual sequence of bytes in each Buffer. The targetStart is an integer specifying the offset within target at which to begin comparison, by default is 0. The targetEnd is an integer specifying the offset within target at which to end comparison, by default is target.length. The sourceStart is an integer specifying the offset within buffer at which to begin comparison, by default is 0. The sourceEnd is an integer specifying the offset within buffer at which to end comparison (not inclusive), by default is buf.length.

buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])

Copies data from a region of buffer to a region in target, even if the target memory region overlaps with buffer. The target parameter is a Buffer or Uint8Array to copy into.

The targetStart is an integer specifying the offset within target at which to begin writing, by default is 0. The sourceStart is an integer specifying the offset within buffer from which to begin copying, by default is 0. The sourceEnd is an integer specifying the offset within buffer at which to stop copying (not inclusive) by default is buf.length.

buf.equals(otherBuffer)

A boolean value, returns true if both Buffer and otherBuffer have exactly the same bytes.

buf.fill(value[, offset[, end]][, encoding])

Fills the Buffer with the specified value. If the offset and end are not specified, the entire Buffer will be filled. The value is coerced to uint32 if it is not a string, Buffer, or integer. If the resulting integer is greater than 255, the Buffer will be filled with value and 255.

buf.includes(value[, byteOffset][, encoding])

Equivalent to buf.indexOf() !== -1, returns true if the value was found in Buffer.

buf.indexOf(value[, byteOffset][, encoding])

Returns an integer which is the index of the first occurrence of value in Buffer, or -1 if Buffer does not contain value. The value can be a string with specified encoding (by default utf8), Buffer, Unit8Array, or a number between 0 and 255.

buf.lastIndexOf(value[, byteOffset][, encoding])

The same as buf.indexOf(), except the last occurrence of the value is found instead of the first occurrence. The value can be a string, Buffer, or integer between 1 and 255. If the value is an empty string or empty Buffer, byteOffset will be returned.

buf.length

Returns the number of bytes in Buffer.

buf.readIntBE(offset, byteLength)

Reads the byteLength from buf at the specified offset and interprets the result as a big-endian, two's complement signed value supporting up to 48 bits of accuracy. The byteLength parameter is an integer between 1 and 6 specifying the number of bytes to read.

The similar methods are also supported: buf.readInt8([offset]), buf.readInt16BE([offset]), buf.readInt32BE([offset]).

buf.readIntLE(offset, byteLength)

Reads the byteLength from buf at the specified offset and interprets the result as a little-endian, two's complement signed value supporting up to 48 bits of accuracy. The byteLength parameter is an integer between 1 and 6 specifying the number of bytes to read.

The similar methods are also supported: buf.readInt8([offset]), buf.readInt16LE([offset]), buf.readInt32LE([offset]).

buf.readUIntBE(offset, byteLength)

Reads the byteLength from buf at the specified offset and interprets the result as a big-endian integer supporting up to 48 bits of accuracy. The byteLength parameter is an integer between 1 and 6 specifying the number of bytes to read.

The similar methods are also supported: buf.readUInt8([offset]), buf.readUInt16BE([offset]), buf.readUInt32BE([offset]).

buf.readUIntLE(offset, byteLength)

Reads the byteLength from buf at the specified offset and interprets the result as a little-endian integer supporting up to 48 bits of accuracy. The byteLength parameter is an integer between 1 and 6 specifying the number of bytes to read.

The similar methods are also supported: buf.readUInt8([offset]), buf.readUInt16LE([offset]), buf.readUInt32LE([offset]).

buf.readDoubleBE([offset])

Reads a 64-bit, big-endian double from buf at the specified offset.

buf.readDoubleLE([offset])

Reads a 64-bit, little-endian double from buf at the specified offset.

buf.readFloatBE([offset])

Reads a 32-bit, big-endian float from buf at the specified offset.

buf.readFloatLE([offset])

Reads a 32-bit, little-endian float from buf at the specified offset.

buf.subarray([start[, end]])

Returns a new buf that references the same memory as the original, but offset and cropped by start and end. If end is greater than buf.length, the same result as that of end equal to buf.length is returned.

buf.slice([start[, end]])

Returns a new buf that references the same memory as the original, but offset and cropped by the start and end values. The method is not compatible with the Uint8Array.prototype.slice(), which is a superclass of Buffer. To copy the slice, use Uint8Array.prototype.slice().

buf.swap16()

Interprets buf as an array of unsigned 16-bit numbers and swaps the byte order in-place. Throws an error if buf.length is not a multiple of 2.

buf.swap32()

Interprets buf as an array of unsigned 32-bit numbers and swaps the byte order in-place. Throws an error if buf.length is not a multiple of 4.

buf.swap64()

Interprets buf as an array of 64-bit numbers and swaps byte order in-place. Throws an error if buf.length is not a multiple of 8.

buf.toJSON()

Returns a JSON representation of buf. JSON.stringify() implicitly calls this function when stringifying a Buffer instance.

buf.toString([encoding[, start[, end]]])

Decodes buf to a string according to the specified character encoding which can be utf8, hex, base64, base64url. The start and end parameters may be passed to decode only a subset of Buffer.

buf.write(string[, offset[, length]][, encoding])

Writes a string to buf at offset according to the character encoding. The length parameter is the number of bytes to write. If Buffer did not contain enough space to fit the entire string, only part of string will be written, however, partially encoded characters will not be written. The encoding can be utf8, hex, base64, base64url.

buf.writeIntBE(value, offset, byteLength)

Writes byteLength bytes of value to buf at the specified offset as big-endian. Supports up to 48 bits of accuracy. The byteLength parameter is an integer between 1 and 6 specifying the number of bytes to read.

The following similar methods are also supported: buf.writeInt8, buf.writeInt16BE, buf.writeInt32BE.

buf.writeIntLE(value, offset, byteLength)

Writes byteLength bytes of value to buf at the specified offset as little-endian. Supports up to 48 bits of accuracy. The byteLength parameter is an integer between 1 and 6 specifying the number of bytes to read.

The following similar methods are also supported: buf.writeInt8, buf.writeInt16LE, buf.writeInt32LE.

buf.writeUIntBE(value, offset, byteLength)

The following similar methods are also supported: buf.writeUInt8, buf.writeUInt16BE, buf.writeUInt32BE.

buf.writeUIntLE(value, offset, byteLength)

The following similar methods are also supported: buf.writeUInt8, buf.writeUInt16LE, buf.writeUInt32LE.

buf.writeDoubleBE(value, [offset])

Writes the value to buf at the specified offset as big-endian.

buf.writeDoubleLE(value, [offset])

Writes the value to buf at the specified offset as little-endian.

buf.writeFloatBE(value, [offset])

Writes the value to buf at the specified offset as big-endian.

buf.writeFloatLE(value, [offset])

Writes the value to buf at the specified offset as little-endian.

Crypto

crypto.createHash()

crypto.createHmac()

Since 0.7.0, extended crypto API is available as a global crypto object.

The Crypto module provides cryptographic functionality support. The Crypto module object is returned by require('crypto').

crypto.createHash(algorithm): Creates and returns a Hash object that can be used to generate hash digests using the given algorithm. The algorithm can be md5, sha1, and sha256.
crypto.createHmac(algorithm, secret key): Creates and returns an HMAC object that uses the given algorithm and secret key. The algorithm can be md5, sha1, and sha256.

Hash

hash.update()

hash.digest()

hash.update(data): Updates the hash content with the given data.
hash.digest([encoding]): Calculates the digest of all of the data passed using hash.update(). The encoding can be hex, base64, and base64url. If encoding is not provided, a Buffer object (0.4.4) is returned.
Before version (0.4.4), a byte string was returned instead of a Buffer object.
hash.copy(): Makes a copy of the current state of the hash (since 0.7.12).

>> var cr = require('crypto')
undefined

>> cr.createHash('sha1').update('A').update('B').digest('base64url')
'BtlFlCqiamG-GMPiK_GbvKjdK10'

HMAC

hmac.update()

hmac.digest()

hmac.update(data): Updates the HMAC content with the given data.
hmac.digest([encoding]): Calculates the HMAC digest of all of the data passed using hmac.update(). The encoding can be hex, base64, and base64url. If encoding is not provided, a Buffer object (0.4.4) is returned.
Before version 0.4.4, a byte string was returned instead of a Buffer object.

>> var cr = require('crypto')
undefined

>> cr.createHmac('sha1', 'secret.key').update('AB').digest('base64url')
'Oglm93xn23_MkiaEq_e9u8zk374'

File System

fs.accessSync()

fs.appendFileSync()

File Access Constants

File System Flags

The File System module provides operations with files.

The module object is returned by require('fs'). Since 0.3.9, promissified versions of file system methods are available through require('fs').promises object:

> var fs = require('fs').promises;
undefined
> fs.readFile("/file/path").then((data)=>console.log(data))
<file data>

accessSync(path[, mode])

Synchronously tests permissions for a file or directory specified in the path (0.3.9). If the check fails, an error will be returned, otherwise, the method will return undefined.

mode

an optional integer that specifies the accessibility checks to be performed, by default is fs.constants.F_OK

try {
    fs.accessSync('/file/path', fs.constants.R_OK | fs.constants.W_OK);
    console.log('has access');
} catch (e) {
    console.log('no access');)
}

appendFileSync(filename, data[, options])

Synchronously appends specified data to a file with provided filename. The data is expected to be a string or a Buffer object (0.4.4). If the file does not exist, it will be created. The options parameter is expected to be an object with the following keys:

mode: mode option, by default is 0o666
flag: file system flag, by default is a

closeSync(fd)

Closes the fd file descriptor represented by an integer used by the method. Returns undefined.

existsSync(path)

Boolean value, returns true if the specified path exists. (0.8.2)

fstatSync(fd)

Retrieves the fs.Stats object for the file descriptor (0.7.7). The fd parameter is an integer representing the file descriptor used by the method.

lstatSync(path[, options])

Synchronously retrieves the fs.Stats object for the symbolic link referred to by path (0.7.1). The options parameter is expected to be an object with the following keys:

throwIfNoEntry: a boolean value which indicates whether an exception is thrown if no file system entry exists, rather than returning undefined, by default is false.

mkdirSync(path[, options])

Synchronously creates a directory at the specified path (0.4.2). The options parameter is expected to be an integer that specifies the mode, or an object with the following keys:

mode: mode option, by default is 0o777.

openSync(path[, flags[, mode]])

Returns an integer representing the file descriptor for the opened file path (0.7.7).

flags: file system flag, by default is r
mode: mode option, by default is 0o666

promises.open(path[, flags[, mode]])

Returns a FileHandle object representing the opened file path (0.7.7).

flags: file system flag, by default is r
mode: mode option, by default is 0o666

readdirSync(path[, options])

Synchronously reads the contents of a directory at the specified path (0.4.2). The options parameter is expected to be a string that specifies encoding or an object with the following keys:

encoding: encoding, by default is utf8. The encoding can be utf8 and buffer (0.4.4).
withFileTypes: if set to true, the files array will contain fs.Dirent objects, by default is false.

readFileSync(filename[, options])

Synchronously returns the contents of the file with provided filename. The options parameter holds string that specifies encoding. If an encoding is specified, a string is returned, otherwise, a Buffer object (0.4.4) is returned.

Before version 0.4.4, a byte string was returned if encoding was not specified.

Otherwise, options is expected to be an object with the following keys:

encoding: encoding, by default is not specified. The encoding can be utf8, hex (0.4.4), base64 (0.4.4), base64url (0.4.4).
flag: file system flag, by default is r

>> var fs = require('fs')
undefined
>> var file = fs.readFileSync('/file/path.tar.gz')
undefined
>> var gzipped = file.slice(0,2).toString('hex') === '1f8b'; gzipped
true

readlinkSync(path[, options])

Synchronously gets the contents of the symbolic link path using readlink(2) (0.8.7). The options argument can be a string specifying an encoding, or an object with encoding property specifying the character encoding to use. If the encoding is buffer, the result is returned as a Buffer object, otherwise as a string.

readSync(fd, buffer, offset[, length[, position]])

Reads the content of a file path using file descriptor fd, returns the number of bytes read (0.7.7).

buffer: the buffer value can be a Buffer, TypedArray, or DataView
offset: is an integer representing the position in buffer to write the data to
length: is an integer representing the number of bytes to read
position: specifies where to begin reading from in the file, the value can be integer or null, by default is null. If position is null, data will be read from the current file position, and the file position will be updated. If position is an integer, the file position will be unchanged

realpathSync(path[, options])

Synchronously computes the canonical pathname by resolving ., .. and symbolic links using realpath(3). The options argument can be a string specifying an encoding, or an object with an encoding property specifying the character encoding to use for the path passed to the callback (0.3.9).

renameSync(oldPath, newPath)

Synchronously changes the name or location of a file from oldPath to newPath (0.3.4).

>> var fs = require('fs')
undefined
>> var file = fs.renameSync('hello.txt', 'HelloWorld.txt')
undefined

rmdirSync(path)

Synchronously removes a directory at the specified path (0.4.2).

statSync(path,[ options])

Synchronously retrieves the fs.Stats object for the specified path (0.7.1). The path can be a string or buffer. The options parameter is expected to be an object with the following keys:

throwIfNoEntry: a boolean value which indicates whether an exception is thrown if no file system entry exists rather than returning undefined, by default is true.

symlinkSync(target, path)

Synchronously creates the link called path pointing to target using symlink(2) (0.3.9). Relative targets are relative to the link’s parent directory.

unlinkSync(path)

Synchronously unlinks a file by path (0.3.9).

writeFileSync(filename, data[, options])

Synchronously writes data to a file with provided filename. The data is expected to be a string or a Buffer object (0.4.4). If the file does not exist, it will be created, if the file exists, it will be replaced. The options parameter is expected to be an object with the following keys:

mode: mode option, by default is 0o666
flag: file system flag, by default is w

>> var fs = require('fs')
undefined
>> var file = fs.writeFileSync('hello.txt', 'Hello world')
undefined

writeSync(fd, buffer, offset[, length[, position]])

Writes a buffer to a file using file descriptor, returns the number of bytes written (0.7.7).

fd: an integer representing the file descriptor
buffer: the buffer value can be a Buffer, TypedArray, or DataView
offset: is an integer that determines the part of the buffer to be written, by default 0
length: is an integer specifying the number of bytes to write, by default is an offset of Buffer.byteLength
position: refers to the offset from the beginning of the file where this data should be written, can be an integer or null, by default is null. See also pwrite(2).

writeSync(fd, string[, position[, encoding]])

Writes a string to a file using file descriptor fd, returns the number of bytes written (0.7.7).

fd: is an integer representing a file descriptor
position: refers to the offset from the beginning of the file where this data should be written, can be an integer or null, by default is null. See also pwrite(2)
encoding: is a string, by default is utf8

fs.Dirent

fs.Dirent is a representation of a directory entry — a file or a subdirectory. When readdirSync() is called with the withFileTypes option, the resulting array contains fs.Dirent objects.

dirent.isBlockDevice() — returns true if the fs.Dirent object describes a block device.
dirent.isCharacterDevice() — returns true if the fs.Dirent object describes a character device.
dirent.isDirectory() — returns true if the fs.Dirent object describes a file system directory.
dirent.isFIFO() — returns true if the fs.Dirent object describes a first-in-first-out (FIFO) pipe.
dirent.isFile() — returns true if the fs.Dirent object describes a regular file.
dirent.isSocket() — returns true if the fs.Dirent object describes a socket.
dirent.isSymbolicLink() — returns true if the fs.Dirent object describes a symbolic link.
dirent.name — the name of the file fs.Dirent object refers to.

fs.FileHandle

filehandle.write(buf)

filehandle.write(str)

The FileHandle object is an object wrapper for a numeric file descriptor (0.7.7). Instances of the FileHandle object are created by the fs.promises.open() method. If a FileHandle is not closed using the filehandle.close() method, it will try to automatically close the file descriptor, helping to prevent memory leaks. Please do not rely on this behavior because it can be unreliable. Instead, always explicitly close a FileHandle.

filehandle.close()

Closes the file handle after waiting for any pending operation on the handle to complete. Returns a promise, fulfills with undefined upon success.

filehandle.fd

The numeric file descriptor managed by the FileHandle object.

filehandle.read(buffer, offset[, length[, position]])

Reads data from the file and stores that in the given buffer.

buffer: a buffer that will be filled with the file data read, the value can be a Buffer, TypedArray, or DataView
offset: is an integer representing the location in the buffer at which to start filling
length: is an integer representing the number of bytes to read
position: the location where to begin reading data from the file, the value can be integer, null. If null, data will be read from the current file position and the position will be updated. If position is an integer, the current file position will remain unchanged.

Returns a Promise which fulfills upon success with an object with two properties:

bytesRead: is an integer representing the number of bytes read
buffer: is a reference to the passed argument in buffer, can be Buffer, TypedArray, or DataView

filehandle.stat()

Fulfills with an fs.Stats for the file, returns a promise.

filehandle.write(buffer, offset[, length[, position]])

Writes a buffer to the file.

buffer: the buffer value can be a Buffer, TypedArray, or DataView
offset: is an integer representing the start position from within buffer where the data to write begins
length: is an integer representing the number of bytes from buffer to write, by default is an offset of Buffer.byteLength
position: the offset from the beginning of the file where the data from buffer should be written, can be an integer or null, by default is null. If position is not a number, the data will be written at the current position. See the POSIX pwrite(2) documentation for details.

Returns a Promise which is resolved with an object containing two properties:

bytesWritten: is an integer representing the number of bytes written
buffer: a reference to the buffer written, can be a Buffer, TypedArray, or DataView

It is unsafe to use filehandle.write() multiple times on the same file without waiting for the promise to be resolved or rejected.

filehandle.write(string[, position[, encoding]])

Writes a string to the file.

position: the offset from the beginning of the file where the data from buffer should be written, can be an integer or null, by default is null. If position is not a number, the data will be written at the current position. See the POSIX pwrite(2) documentation for details.
encoding: the expected encoding of the string, by default utf8

Returns a Promise which is resolved with an object containing two properties:

bytesWritten: is an integer representing the number of bytes written
buffer: a reference to the buffer written, can be a Buffer, TypedArray, or DataView

It is unsafe to use filehandle.write() multiple times on the same file without waiting for the promise to be resolved or rejected.

fs.Stats

The fs.Stats object provides information about a file. The object is returned from fs.statSync() and fs.lstatSync().

stats.isBlockDevice() — returns true if the fs.Stats object describes a block device.
stats.isDirectory() — returns true if the fs.Stats object describes a file system directory.
stats.isFIFO() — returns true if the fs.Stats object describes a first-in-first-out (FIFO) pipe.
stats.isFile() — returns true if the fs.Stats object describes a regular file.
stats.isSocket() — returns true if the fs.Stats object describes a socket.
stats.isSymbolicLink() — returns true if the fs.Stats object describes a symbolic link.
stats.dev — the numeric identifier of the device containing the file.
stats.ino — the file system specific Inode number for the file.
stats.mode — a bit-field describing the file type and mode.
stats.nlink — the number of hard-links that exist for the file.
stats.uid — the numeric user identifier of the user that owns the file (POSIX).
stats.gid — the numeric group identifier of the group that owns the file (POSIX).
stats.rdev — the numeric device identifier if the file represents a device.
stats.size — the size of the file in bytes.
stats.blksize — the file system block size for i/o operations.
stats.blocks — the number of blocks allocated for this file.
stats.atimeMs — the timestamp indicating the last time this file was accessed expressed in milliseconds since the POSIX Epoch.
stats.mtimeMs — the timestamp indicating the last time this file was modified expressed in milliseconds since the POSIX Epoch.
stats.ctimeMs — the timestamp indicating the last time this file was changed expressed in milliseconds since the POSIX Epoch.
stats.birthtimeMs — the timestamp indicating the creation time of this file expressed in milliseconds since the POSIX Epoch.
stats.atime — the timestamp indicating the last time this file was accessed.
stats.mtime — the timestamp indicating the last time this file was modified.
stats.ctime — the timestamp indicating the last time this file was changed.
stats.birthtime — the timestamp indicating the creation time of this file.

File Access Constants

The access() method can accept the following flags. These flags are exported by fs.constants:

F_OK — indicates that the file is visible to the calling process, used by default if no mode is specified
R_OK — indicates that the file can be read by the calling process
W_OK — indicates that the file can be written by the calling process
X_OK — indicates that the file can be executed by the calling process

File System Flags

The flag option can accept the following values:

a — open a file for appending. The file is created if it does not exist
ax — the same as a but fails if the file already exists
a+ — open a file for reading and appending. If the file does not exist, it will be created
ax+ — the same as a+ but fails if the file already exists
as — open a file for appending in synchronous mode. If the file does not exist, it will be created
as+ — open a file for reading and appending in synchronous mode. If the file does not exist, it will be created
r — open a file for reading. An exception occurs if the file does not exist
r+ — open a file for reading and writing. An exception occurs if the file does not exist
rs+ — open a file for reading and writing in synchronous mode. Instructs the operating system to bypass the local file system cache
w — open a file for writing. If the file does not exist, it will be created. If the file exists, it will be replaced
wx — the same as w but fails if the file already exists
w+ — open a file for reading and writing. If the file does not exist, it will be created. If the file exists, it will be replaced
wx+ — the same as w+ but fails if the file already exists

Query String

querystring.decode()

querystring.encode()

querystring.escape()

querystring.parse()

querystring.stringify()

querystring.unescape()

The Query String module provides support for parsing and formatting URL query strings (0.4.3). The Query String module object is returned by require('querystring').

querystring.decode()

is an alias for querystring.parse().

querystring.encode()

is an alias for querystring.stringify().

querystring.escape(string)

Performs URL encoding of the given string, returns an escaped query string. The method is used by querystring.stringify() and should not be used directly.

querystring.parse(string[, separator[, equal[, options]]])

Parses the query string URL and returns an object.

The separator parameter is a substring for delimiting key and value pairs in the query string, by default is “&”.

The equal parameter is a substring for delimiting keys and values in the query string, by default is “=”.

The options parameter is expected to be an object with the following keys:

decodeURIComponent function: Function used to decode percent-encoded characters in the query string, by default is querystring.unescape()
maxKeys number: the maximum number of keys to parse, by default is 1000. The 0 value removes limitations for counting keys.

By default, percent-encoded characters within the query string are assumed to use the UTF-8 encoding, invalid UTF-8 sequences will be replaced with the U+FFFD replacement character.

For example, for the following query string

'foo=bar&abc=xyz&abc=123'

the output will be:

{
  foo: 'bar',
  abc: ['xyz', '123']
}

querystring.stringify(object[, separator[, equal[, options]]])

Serializes an object and returns a URL query string.

The separator parameter is a substring for delimiting key and value pairs in the query string, by default is “&”.

The equal parameter is a substring for delimiting keys and values in the query string, by default is “=”.

The options parameter is expected to be an object with the following keys:

encodeURIComponent function: The function to use when converting URL-unsafe characters to percent-encoding in the query string, by default is querystring.escape().

By default, characters that require percent-encoding within the query string are encoded as UTF-8. If other encoding is required, then encodeURIComponent option should be specified.

For example, for the following command

querystring.stringify({ foo: 'bar', baz: ['qux', 'quux'], 123: '' });

the query string will be:

'foo=bar&baz=qux&baz=quux&123='

querystring.unescape(string)

Performs decoding of URL percent-encoded characters of the string, returns an unescaped query string. The method is used by querystring.parse() and should not be used directly.

XML

xml.parse()

xml.c14n()

xml.exclusiveC14n()

xml.serialize()

xml.serializeToString()

XMLDoc

XMLNode

XMLAttr

The XML module allows working with XML documents (since 0.7.10). The XML module object is returned by require('xml').

Example:

const xml = require("xml");
let data = `<note><to b="bar" a= "foo" >Tove</to><from>Jani</from></note>`;
let doc = xml.parse(data);

console.log(doc.note.to.$text) /* 'Tove' */
console.log(doc.note.to.$attr$b) /* 'bar' */
console.log(doc.note.$tags[1].$text) /* 'Jani' */

let dec = new TextDecoder();
let c14n = dec.decode(xml.exclusiveC14n(doc.note));
console.log(c14n) /* '<note><to a="foo" b="bar">Tove</to><from>Jani</from></note>' */

c14n = dec.decode(xml.exclusiveC14n(doc.note.to));
console.log(c14n) /* '<to a="foo" b="bar">Tove</to>' */

c14n = dec.decode(xml.exclusiveC14n(doc.note, doc.note.to /* excluding 'to' */));
console.log(c14n) /* '<note><from>Jani</from></note>' */

parse(string | Buffer)

Parses a string or Buffer for an XML document, returns an XMLDoc wrapper object representing the parsed XML document.

c14n(root_node[, excluding_node])

Canonicalizes root_node and its children according to Canonical XML Version 1.1. The root_node can be XMLNode or XMLDoc wrapper object around XML structure. Returns Buffer object that contains canonicalized output.

excluding_node: allows omitting from the output a part of the document

exclusiveC14n(root_node[, excluding_node[, withComments [,prefix_list]]])

Canonicalizes root_node and its children according to Exclusive XML Canonicalization Version 1.0.

root_node: is XMLNode or XMLDoc wrapper object around XML structure
excluding_node: allows omitting from the output a part of the document corresponding to the node and its children
withComments: a boolean value, false by default. If true, canonicalization corresponds to Exclusive XML Canonicalization Version 1.0. Returns Buffer object that contains canonicalized output.
prefix_list: an optional string with a space separated namespace prefixes for namespaces that should also be included into the output

serialize()

The same as xml.c14n() (since 0.7.11).

serializeToString()

The same as xml.c14n() except it returns the result as a string (since 0.7.11).

XMLDoc

An XMLDoc wrapper object around XML structure, the root node of the document.

doc.$root: the document's root by its name or undefined
doc.abc: the first root tag named abc as XMLNode wrapper object

XMLNode

An XMLNode wrapper object around XML tag node.

node.abc: the same as node.$tag$abc
node.$attr$abc: the node's attribute value of abc, writable since 0.7.11
node.$attr$abc=xyz: the same as node.setAttribute('abc', xyz) (since 0.7.11)
node.$attrs: an XMLAttr wrapper object for all attributes of the node
node.$name: the name of the node
node.$ns: the namespace of the node
node.$parent: the parent node of the current node
node.$tag$abc: the first child tag of the node named abc, writable since 0.7.11
node.$tags: an array of all children tags
node.$tags = [node1, node2, ...]: the same as node.removeChildren(); node.addChild(node1); node.addChild(node2) (since 0.7.11).
node.$tags$abc: all children tags named abc of the node, writable since 0.7.11
node.$text: the content of the node, writable since 0.7.11
node.$text = 'abc': the same as node.setText('abc') (since 0.7.11)
node.addChild(nd): adds XMLNode as a child to node (since 0.7.11). nd is recursively copied before adding to the node
node.removeAllAttributes(): removes all attributes of the node (since 0.7.11)
node.removeAttribute(attr_name): removes the attribute named attr_name (since 0.7.11)
node.removeChildren(tag_name): removes all the children tags named tag_name (since 0.7.11). If tag_name is absent, all children tags are removed
node.removeText(): removes the node's text value (0.7.11)
node.setAttribute(attr_name, value): sets a value for an attr_name (since 0.7.11). When the value is null, the attribute named attr_name is deleted
node.setText(value): sets a text value for the node (since 0.7.11). When the value is null, the text of the node is deleted.

XMLAttr

An XMLAttrs wrapper object around XML node attributes.

attr.abc: the attribute value of abc

zlib

zlib.deflateRawSync()

zlib.deflateSync()

zlib.inflateRawSync()

zlib.inflateSync()

The zlib module provides compression functionality using the “deflate” and “inflate” algorithms (since 0.7.12). The zlib module object is returned by require('zlib').

deflateRawSync(string | Buffer[, options]): Compresses data using the “deflate” algorithm provided as a string or Buffer and does not append a zlib header. The buffer value can be a Buffer, TypedArray, or DataView. Options is an optional object that contains zlib_options. Returns Buffer instance that contains the compressed data.
deflateSync(string | Buffer[, options]): Compresses data using the “deflate” algorithm provided as a string or Buffer. The Buffer value can be a Buffer, TypedArray, or DataView. Options is an optional object that contains zlib_options. Returns Buffer instance that contains the compressed data.
inflateRawSync(string | Buffer): Decompresses a raw stream by using the “deflate” algorithm. Returns Buffer instance that contains the decompressed data.
inflateSync(string | Buffer): Decompresses a stream by using the “deflate” algorithm. Returns Buffer instance that contains the decompressed data.

zlib options

chunkSize — is an integer, by default is 1024
dictionary — is a Buffer, TypedArray, or DataView. by default is empty
level — is an integer, compression only, see zlib_compression_levels
memLevel — is an integer from 1 to 9, compression only
strategy — is an integer, compression only, see zlib_compression_strategy
windowBits — is an integer from -15 to -9 for raw data, from 9 to 15 for an ordinary stream

zlib compression levels

Name	Description
`zlib.constants.Z_NO_COMPRESSION`	no compression
`zlib.constants.Z_BEST_SPEED`	fastest, produces the least compression
`zlib.constants.Z_DEFAULT_COMPRESSION`	trade-off between speed and compression
`zlib.constants.Z_BEST_COMPRESSION`	slowest, produces the most compression

zlib compression strategy

Name	Description
`zlib.constants.Z_FILTERED`	Filtered strategy: for the data produced by a filter or predictor
`zlib.constants.Z_HUFFMAN_ONLY`	Huffman-only strategy: only Huffman encoding, no string matching
`zlib.constants.Z_RLE`	Run Length Encoding strategy: limit match distances to one, better compression of PNG image data
`zlib.constants.Z_FIXED`	Fixed table strategy: prevents the use of dynamic Huffman codes, a simpler decoder for special applications
`zlib.constants.Z_DEFAULT_STRATEGY`	Default strategy, suitable for general purpose compression