Reference (original) (raw)

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 inECMAScript specification. List of all njs properties and methods can be found inCompatibility.

nginx objects

HTTP Request

r.args{}
r.done()
r.error()
r.finish()
r.headersIn{}
r.headersOut{}
r.httpVersion
r.internal
r.internalRedirect()
r.log()
r.method
r.parent
r.remoteAddress
r.requestBody
r.requestBuffer
r.requestText
r.rawHeadersIn[]
r.rawHeadersOut[]
r.responseBody
r.responseBuffer
r.responseText
r.return()
r.send()
r.sendBuffer()
r.sendHeader()
r.setReturnValue()
r.status
r.subrequest()
r.uri
r.rawVariables{}
r.variables{}
r.warn()

The HTTP request object is available only in thengx_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 theQuery String module and with the$argsvariable, 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 objectreturns the first value for a given key, case-insensitive, without percent-decoding.

To convert r.args back to a string, the Query Stringstringifymethod can be used.

r.done()

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

r.error(`_string_`)

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

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

r.finish()

finishes sending a response to the client

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.

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:

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 forinternallocations

r.internalRedirect(`_uri_`)

performs aninternal redirectto 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_PHASEfor ordinary locations and from NGX_HTTP_REWRITE_PHASEfor named locations. As a result, a redirect to a named location does not check client_max_body_sizelimit. See dev guidefor more details. Redirected requests become internal and can access theinternallocations. 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 forhttp orstreamcan 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 ahardcodedmaximum 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 in0.5.0and was removed in 0.8.0. The r.requestBuffer orr.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 byclient_max_body_size, and a sufficient buffer size should be set usingclient_body_buffer_size. The property is available only in thejs_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.

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.

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 in0.5.0and was removed in 0.8.0. The r.responseBufferor the r.responseTextproperty 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 thesubrequest_output_buffer_sizedirective.

r.responseText

the same as r.responseBufferbut 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 thejs_body_filter function.

sends the HTTP headers to the client

r.setReturnValue(`_value_`)

sets the return value of thejs_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 andoptions, and installs an optional completion callback.

Asubrequestshares its input headers with the client request. To send headers different from original headers to a proxied server, theproxy_set_headerdirective can be used. To send a completely new set of headers to a proxied server, theproxy_pass_request_headersdirective 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 objectis 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 URIin 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.confand 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$request_idvariable is only accessed from njs, it has a new value every time it is evaluated. But, when the$request_idis 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:

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 ahardcodedmaximum line length limit, only first 2048 bytes of the string can be logged.

Stream Session

s.allow()
s.decline()
s.deny()
s.done()
s.error()
s.log()
s.off()
s.on()
s.remoteAddress
s.rawVariables{}
s.send()
s.sendDownstream()
s.sendUpstream()
s.status
s.setReturnValue()
s.variables{}
s.warn()

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

s.allow()

an alias tos.done(0)(0.2.4)

s.decline()

an alias tos.done(-5)(0.2.4)

s.deny()

an alias tos.done(403)(0.2.4)

s.done([`_code_`])

sets an exit code for the currentphase handler to a code value, by default 0. The actual finalization happens when the js handler is completed and all pending events, for example, fromngx.fetch() orsetTimeout(), are processed (0.2.4).

Possible code values:

s.error(`_string_`)

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

As nginx has ahardcodedmaximum 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 ahardcodedmaximum 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 callbackfor 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), wheredata 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$statusvariable, read only (since 0.5.2)

s.setReturnValue(`_value_`)

sets the return value of thejs_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 ahardcodedmaximum line length limit, only first 2048 bytes of the string can be logged.

Periodic Session

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

PeriodicSession.rawVariables{}

nginx variables as Buffers, writable.

PeriodicSession.variables{}

nginx variables object, writable.

Headers

The Headers interface of theFetch APIis available since 0.5.1.

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

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:

Appends a new value into an existing header in theHeaders object, or adds the header if it does not already exist (since 0.7.10).

Deletes a header from the Headers object (since 0.7.10).

Returns a string containing the values of all headers with the specified name separated by a comma and a space.

Returns an array containing the values of all headers with the specified name.

Executes a provided function once for each key/value pair in the Headers object (since 0.7.10).

Returns a boolean value indicating whether a header with the specified name exists.

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
Request.headers
Request.json()
Request.method
Request.mode
Request.text()
Request.url

The Request interface of theFetch APIis available since 0.7.10.

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

Request[`_resource_`[,`_options_`]])

Creates a Request object to fetch that can be passed later tongx.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, trueif 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.

The Headers read-only object associated with theRequest.

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.bodyUsed
Response.headers
Response.json()
Response.ok
Response.redirected
Response.status
Response.statusText
Response.text()
Response.type
Response.url

The Response interface is available since0.5.1.

A new Response object can be created using theResponse() 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, trueif the body was read.

The Headers read-only object associated with theResponse.

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, trueif the response was successful (status codes between 200–299).

redirected

A boolean value, trueif 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

ngx.build
ngx.conf_file_path
ngx.conf_prefix
ngx.error_log_path
ngx.fetch()
ngx.log()
ngx.prefix
ngx.version
ngx.version_number
ngx.worker_id

The ngx global object is available since 0.5.0.

ngx.build

a string containing an optional nginx build name, corresponds to the--build=nameargument 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 tonginx 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 currenterror 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 aresolver. If the https:// scheme is specified, thejs_fetch_trusted_certificatedirective 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

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, andngx.ERR.

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

ngx.prefix

a string containing the file path tonginx 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 theworker_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 inhttporstream.

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

ngx.shared.SharedDict.add(`_key_`,`_value_` [,`_timeout_`])

Sets the valuefor 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 thejs_shared_dict_zone directive inhttporstream(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 ofjs_shared_dict_zone directive inhttporstream.

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 keyor undefined if there is none.

ngx.shared.SharedDict.has(`_key_`)

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

ngx.shared.SharedDict.incr(`_key_`,`_delta_`[[,`_init_`], `_timeout_`]))

Increments the integer value associated with the keyby 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.

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

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 withtype=number parameter of thejs_shared_dict_zone directive inhttporstream.

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 ofjs_shared_dict_zone directive inhttporstream.

ngx.shared.SharedDict.pop(`_key_`)

Removes the item associated with the specified keyfrom the SharedDict dictionary, returns the value associated with the keyor undefined if there is none.

ngx.shared.SharedDict.replace(`_key_`,`_value_`)

Replaces the valuefor 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).

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

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 ofjs_shared_dict_zone directive inhttporstream.

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 byconsole.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 typedArraybut with its contents replaced with the newly generated random numbers. Possible values:

typedArray

can beInt8Array,Int16Array,Uint16Array,Int32Array, orUint32Array

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

Encrypts datausing the providedalgorithm andkey. 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:

key

a CryptoKey that contains the key to be used for encryption

data

anArrayBuffer,TypedArray, orDataViewthat 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.

key

a CryptoKeythat contains the key to be used for decryption. If RSA-OAEP is used, this is theprivateKey property of theCryptoKeyPair object.

data

anArrayBuffer,TypedArray, orDataViewthat 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 Promisewhich will be fulfilled with anArrayBuffer that contains the derived bits. Possible values:

algorithm

is an object that defines the derivation algorithm to use:

baseKey

is a CryptoKeythat 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 usingсrypto.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:

baseKey

is a CryptoKeythat 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 usingсrypto.subtle.importKey().

derivedKeyAlgorithm

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

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

keyUsages

is an Arraythat 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, orSHA-512

data

is anArrayBuffer,TypedArray, orDataViewthat 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 anArrayBuffer 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

thePKCS #8format

spki

theSubjectPublicKeyInfoformat

jwk

theJSON Web Key(JWK) format (since 0.7.10)

key

the CryptoKeythat 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 CryptoKeyor CryptoKeyPair object. Possible values:

algorithm

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

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

thePKCS #8format

spki

theSubjectPublicKeyInfoformat

jwk

theJSON Web Key(JWK) format (since 0.7.10)

keyData

theArrayBuffer,TypedArray, orDataViewobject 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:

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 Promisethat 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:

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 anArrayBuffer,TypedArray, orDataViewobject 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:

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 anArrayBuffer,TypedArray, orDataViewthat contains the signature to verify

data

is anArrayBuffer,TypedArray, orDataViewobject that contains the data whose signature is to be verified

CryptoKey

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

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'sCryptoKeyPair

public

This key is the public half of an asymmetric algorithm'sCryptoKeyPair.

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

The CryptoKeyPair is a dictionary object of the WebCrypto APIthat 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 asr.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 in0.4.4and 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 behex,base64, andbase64url.

String.prototype.fromBytes(`_start_`[,`_end_`])

the property was made obsolete in0.7.7and 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 in0.7.7and 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 in0.7.7and 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 in0.7.7and was removed in 0.8.0. Before 0.7.7, encoded a string tohex,base64, orbase64url:

'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 in0.7.7and 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

The TextDecoderproduces 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 isTextDecoderOptions dictionary with the property:

fatal

boolean flag indicating ifTextDecoder.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 byTextDecoder(), 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 byTextDecoder(). The buffer can be ArrayBuffer. The options isTextDecodeOptions 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, andfalse 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

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 TextEncoderthat will generate a byte stream with UTF-8 encoding.

TextEncoder.prototype.encode(`_string_`)

Encodes string into a Uint8Arraywith 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 stringconverted to UTF-8

written

the number of bytes modified in the destination Uint8Array

timers

clearTimeout(`_timeout_`)

Cancels a timeout object created by setTimeout().

setTimeout(`_function_`,`_milliseconds_`[,`_argument1_`,`_argumentN_`])

Calls a functionafter a specified number of milliseconds. One or more optional argumentscan be passed to the specified function. Returns a timeout object.

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

t = setTimeout(handler, 12);

// ...

clearTimeout(t);

Global functions

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 ofstringToEncode.

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()
buffer[]
buf.buffer
buf.byteOffset
buf.compare()
buf.copy()
buf.equals()
buf.fill()
buf.includes()
buf.indexOf()
buf.lastIndexOf()
buf.length
buf.readIntBE()
buf.readIntLE()
buf.readUIntBE()
buf.readUIntLE()
buf.readDoubleBE
buf.readDoubleLE()
buf.readFloatBE()
buf.readFloatLE()
buf.subarray()
buf.slice()
buf.swap16()
buf.swap32()
buf.swap64()
buf.toJSON()
buf.toString()
buf.write()
buf.writeIntBE()
buf.writeIntLE()
buf.writeUIntBE()
buf.writeUIntLE()
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 callingbuf.fill(fill). If _fill_ and _encoding_ are specified, the allocated Buffer will be initialized by callingbuf.fill(fill, encoding).

The _fill_ parameter may be a_string_,_Buffer_,_Uint8Array_, or_integer_.

Buffer.allocUnsafe(`_size_`)

The same asBuffer.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 astring,Buffer,TypedArray,DataView, orArrayBuffer. 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. Returns0 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, returnsBuffer.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 beutf8,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 trueif 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 astring,Buffer, orinteger. If the resulting integer is greater than 255, the Buffer will be filled with _value_ and 255.

buf.includes(`_value_`[,`_byteOffset_`][,`_encoding_`])

Equivalent tobuf.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 astring with specified _encoding_(by default _utf8_),Buffer,Unit8Array, or a number between 0 and 255.

buf.lastIndexOf(`_value_`[,`_byteOffset_`][,`_encoding_`])

The same asbuf.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 bufat 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 bufat 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 bufat 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 bufat 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 bufat the specified _offset_.

buf.readDoubleLE([_offset_])

Reads a 64-bit, little-endian double from bufat the specified _offset_.

buf.readFloatBE([_offset_])

Reads a 32-bit, big-endian float from bufat the specified _offset_.

buf.readFloatLE([_offset_])

Reads a 32-bit, little-endian float from bufat the specified _offset_.

buf.subarray([`_start_`[,`_end_`]])

Returns a new bufthat references the same memory as the original, but offset and cropped by_start_ and _end_. If _end_ is greater thanbuf.length, the same result as that of end equal tobuf.lengthis returned.

buf.slice([`_start_`[,`_end_`]])

Returns a new bufthat references the same memory as the original, but offset and cropped by the_start_ and _end_ values. The method is not compatible with theUint8Array.prototype.slice(), which is a superclass of Buffer. To copy the slice, useUint8Array.prototype.slice().

buf.swap16()

Interprets buf as an array of unsigned 16-bit numbers and swaps the byte order in-place. Throws an error ifbuf.lengthis 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 ifbuf.lengthis 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 ifbuf.lengthis 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 bufat _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 bufat 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 bufat 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_`)

Writes _byteLength_ bytes of _value_to bufat 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.writeUInt8,buf.writeUInt16BE,buf.writeUInt32BE.

buf.writeUIntLE(`_value_`,`_offset_`,`_byteLength_`)

Writes _byteLength_ bytes of _value_to bufat 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.writeUInt8,buf.writeUInt16LE,buf.writeUInt32LE.

buf.writeDoubleBE(`_value_`, [`_offset_`])

Writes the _value_ to bufat the specified _offset_ as big-endian.

buf.writeDoubleLE(`_value_`, [`_offset_`])

Writes the _value_ to bufat the specified _offset_ as little-endian.

buf.writeFloatBE(`_value_`, [`_offset_`])

Writes the _value_ to bufat the specified _offset_ as big-endian.

buf.writeFloatLE(`_value_`, [`_offset_`])

Writes the _value_ to bufat the specified _offset_ as little-endian.

Crypto

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

The Crypto module provides cryptographic functionality support. The Crypto module object is imported using import crypto from '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 bemd5,sha1, andsha256.

crypto.createHmac(`_algorithm_`,`_secret key_`)

Creates and returns an HMAC object that uses the given _algorithm_ and _secret key_. The algorithm can bemd5,sha1, andsha256.

Hash

hash.update(`_data_`)

Updates the hash content with the given _data_.

hash.digest([`_encoding_`])

Calculates the digest of all of the data passed usinghash.update(). The encoding can behex,base64, andbase64url. 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).

import crypto from 'crypto';

crypto.createHash('sha1').update('A').update('B').digest('base64url'); /* BtlFlCqiamG-GMPiK_GbvKjdK10 */

HMAC

hmac.update(`_data_`)

Updates the HMAC content with the given _data_.

hmac.digest([`_encoding_`])

Calculates the HMAC digest of all of the data passed usinghmac.update(). The encoding can behex,base64, andbase64url. 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.

import crypto from 'crypto';

crypto.createHmac('sha1', 'secret.key').update('AB').digest('base64url'); /* Oglm93xn23_MkiaEq_e9u8zk374 */

File System

fs.accessSync()
fs.appendFileSync()
fs.closeSync()
fs.existsSync()
fs.fstatSync()
fs.lstatSync()
fs.mkdirSync()
fs.openSync()
fs.promises.open()
fs.readdirSync()
fs.readFileSync()
fs.readlinkSync()
fs.readSync()
fs.realpathSync()
fs.renameSync()
fs.rmdirSync()
fs.statSync()
fs.symlinkSync()
fs.unlinkSync()
fs.writeFileSync()
fs.writeSync()
fs.writeSync()

The File System module provides operations with files.

The module object is imported using import fs from 'fs'. Since 0.3.9, promissified versions of file system methods are available throughfs.promises object after importing with import fs from 'fs':

import fs from 'fs';

fs.promises.readFile("/file/path").then((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 datato 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, returnstrue 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 aninteger 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 encodingor 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 containfs.Dirent objects, by default is false.

readFileSync(`_filename_`[,`_options_`])

Synchronously returns the contents of the file with provided filename. The options parameter holdsstring 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

import fs from 'fs';

var file = fs.readFileSync('/file/path.tar.gz'); console.log(file.slice(0,2).toString('hex')) /* '1f8b' */

readlinkSync(`_path_`[,`_options_`])

Synchronously gets the contents of the symbolic link pathusingreadlink(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 aBuffer,TypedArray, orDataView

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 beinteger ornull, 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 usingrealpath(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 fromoldPath to newPath(0.3.4).

import fs from 'fs';

fs.renameSync('hello.txt', 'HelloWorld.txt');

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 astring orbuffer. 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 pathpointing to target usingsymlink(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

import fs from 'fs';

fs.writeFileSync('hello.txt', 'Hello world');

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 aBuffer,TypedArray, orDataView

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 ofBuffer.byteLength

position

refers to the offset from the beginning of the file where this data should be written, can be aninteger ornull, by default is null. See alsopwrite(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 aninteger ornull, by default is null. See alsopwrite(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. WhenreaddirSync()is called with thewithFileTypesoption, the resulting array contains fs.Dirent objects.

fs.FileHandle

The FileHandle object is an object wrapper for a numeric file descriptor (0.7.7). Instances of the FileHandle object are created by thefs.promises.open() method. If a FileHandle is not closed using thefilehandle.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 aBuffer,TypedArray, orDataView

offset

is an integerrepresenting the location in the buffer at which to start filling

length

is an integerrepresenting the number of bytes to read

position

the location where to begin reading data from the file, the value can beinteger,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 beBuffer,TypedArray, orDataView

filehandle.stat()

Fulfills with anfs.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 aBuffer,TypedArray, orDataView

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 ofBuffer.byteLength

position

the offset from the beginning of the file where the data from buffer should be written, can be aninteger ornull, by default is null. If position is not a number, the data will be written at the current position. See the POSIXpwrite(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 aBuffer,TypedArray, orDataView

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 aninteger ornull, by default is null. If position is not a number, the data will be written at the current position. See the POSIXpwrite(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 aBuffer,TypedArray, orDataView

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 fromfs.statSync() andfs.lstatSync().

File Access Constants

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

File System Flags

The flag option can accept the following values:

Query String

The Query String module provides support for parsing and formatting URL query strings (0.4.3). The Query String module object is imported usingimport qs from 'querystring'.

querystring.decode()

is an alias forquerystring.parse().

querystring.encode()

is an alias forquerystring.stringify().

querystring.escape(`_string_`)

Performs URL encoding of the given string, returns an escaped query string. The method is used byquerystring.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 isquerystring.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 isquerystring.escape().

By default, characters that require percent-encoding within the query string are encoded as UTF-8. If other encoding is required, thenencodeURIComponent 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 byquerystring.parse()and should not be used directly.

XML

The XML module allows working with XML documents (since 0.7.10). The XML module object is imported usingimport xml from 'xml'.

Example:

import xml from '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) /* 'ToveJani' */

c14n = dec.decode(xml.exclusiveC14n(doc.note.to)); console.log(c14n) /* 'Tove' */

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

parse(`_string_` |`_Buffer_`)

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

c14n(`_rootnode_`[,`_excludingnode_`])

Canonicalizes root_node and its children according toCanonical XML Version 1.1. The root_node can beXMLNode orXMLDoc 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(`_rootnode_`[,`_excludingnode_`[,`_withComments_`[,`_prefixlist_`]]])

Canonicalizes root_node and its children according toExclusive XML Canonicalization Version 1.0.

root_node

isXMLNode orXMLDoc 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 toExclusive 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 asxml.c14n()(since 0.7.11).

serializeToString()

The same asxml.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_ asXMLNode wrapper object

XMLNode

An XMLNode wrapper object around XML tag node.

node.`_abc_`

the same asnode.$tag$abc

node.$attr$`_abc_`

the node's attribute value of _abc_, writable since 0.7.11

node.$attr$`_abc_`=_xyz_

the same asnode.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 asnode.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 asnode.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(`_attrname_`)

removes the attribute named attr_name(since 0.7.11)

node.removeChildren(`_tagname_`)

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(`_attrname_`,`_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

The zlib module provides compression functionality using the “deflate” and “inflate” algorithms (since 0.7.12). The zlib module object is imported usingimport zlib from '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 aBuffer,TypedArray, orDataView.Options is an optional object that containszlib_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 aBuffer,TypedArray, orDataView.Options is an optional object that containszlib_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

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