node-fetch
A light-weight module that brings window.fetch
to Node.js
Motivation
Instead of implementing XMLHttpRequest
in Node.js to run browser-specific Fetch polyfill, why not go from native http
to fetch
API directly? Hence node-fetch
, minimal code for a window.fetch
compatible API on Node.js runtime.
See Matt Andrews' isomorphic-fetch for isomorphic usage (exports node-fetch
for server-side, whatwg-fetch
for client-side).
Features
- Stay consistent with
window.fetch
API. - Make conscious trade-off when following whatwg fetch spec and stream spec implementation details, document known difference.
- Use native promise, but allow substituting it with [insert your favorite promise library].
- Use native stream for body, on both request and response.
- Decode content encoding (gzip/deflate) properly, and convert string output (such as
res.text()
andres.json()
) to UTF-8 automatically. - Useful extensions such as timeout, redirect limit, response size limit, explicit errors for troubleshooting.
Difference from client-side fetch
- See Known Differences for details.
- If you happen to use a missing feature that
window.fetch
offers, feel free to open an issue. - Pull requests are welcomed too!
Install
Stable release (1.x
)
$ npm install node-fetch --save
Next release (2.x
), currently in alpha
$ npm install node-fetch@next --save
Usage
Note that documentation below is up-to-date with 2.x
releases, see 1.x
readme, changelog and 2.x upgrade guide if you want to find out the difference.
;// or// const fetch = require('node-fetch'); // if you are using your own Promise library, set it through fetch.Promise. Eg. // import Bluebird from 'bluebird';// fetch.Promise = Bluebird; // plain text or html ; // json ; // catching network error// 3xx-5xx responses are NOT network errors, and should be handled in then()// you only need one catch() at the end of your promise chain ; // stream// the node.js way is to use stream when possible ; // buffer// if you prefer to cache binary data in full, use buffer()// note that buffer() is a node-fetch only API ; ; // meta ; // post ; // post with stream from file ; const stream = ; ; // post with JSON var body = a: 1 ; ; // post form parameters (x-www-form-urlencoded) ; const params = ;params; ; // post with form-data (detect multipart) ; const form = ;form; ; // post with form-data (custom headers)// note that getHeaders() is non-standard API ; const form = ;form; ; // node 7+ with async function { const res = await ; const json = await res; console;};
See test cases for more examples.
API
fetch(url[, options])
url
A string representing the URL for fetchingoptions
Options for the HTTP(S) request- Returns:
Promise<Response>
Perform an HTTP(S) fetch.
url
should be an absolute url, such as http://example.com/
. A path-relative URL (/file/under/root
) or protocol-relative URL (//can-be-http-or-https.com/
) will result in a rejected promise.
Options
The default values are shown after each option key.
// These properties are part of the Fetch Standard method: 'GET' headers: {} // request headers. format is the identical to that accepted by the Headers constructor (see below) body: null // request body. can be null, a string, a Buffer, a Blob, or a Node.js Readable stream redirect: 'follow' // set to `manual` to extract redirect headers, `error` to reject redirect // The following properties are node-fetch extensions follow: 20 // maximum redirect count. 0 to not follow redirect timeout: 0 // req/res timeout in ms, it resets on redirect. 0 to disable (OS limit applies) compress: true // support gzip/deflate content encoding. false to disable size: 0 // maximum response body size in bytes. 0 to disable agent: null // http(s).Agent instance, allows custom proxy, certificate etc.
Default Headers
If no values are set, the following request headers will be sent automatically:
Header | Value |
---|---|
Accept-Encoding |
gzip,deflate (when options.compress === true ) |
Accept |
*/* |
Connection |
close (when no options.agent is present) |
Content-Length |
(automatically calculated, if possible) |
User-Agent |
node-fetch/1.0 (+https://github.com/bitinn/node-fetch) |
Class: Request
An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the Body interface.
Due to the nature of Node.js, the following properties are not implemented at this moment:
type
destination
referrer
referrerPolicy
mode
credentials
cache
integrity
keepalive
The following node-fetch extension properties are provided:
follow
compress
counter
agent
See options for exact meaning of these extensions.
new Request(input[, options])
(spec-compliant)
input
A string representing a URL, or anotherRequest
(which will be cloned)options
[Options][#fetch-options] for the HTTP(S) request
Constructs a new Request
object. The constructor is identical to that in the browser.
In most cases, directly fetch(url, options)
is simpler than creating a Request
object.
Class: Response
An HTTP(S) response. This class implements the Body interface.
The following properties are not implemented in node-fetch at this moment:
Response.error()
Response.redirect()
type
redirected
trailer
new Response([body[, options]])
(spec-compliant)
body
A string or Readable streamoptions
AResponseInit
options dictionary
Constructs a new Response
object. The constructor is identical to that in the browser.
Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a Response
directly.
response.ok
Convenience property representing if the request ended normally. Will evaluate to true if the response status was greater than or equal to 200 but smaller than 300.
Class: Headers
This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the Fetch Standard are implemented.
new Headers([init])
(spec-compliant)
init
Optional argument to pre-fill theHeaders
object
Construct a new Headers
object. init
can be either null
, a Headers
object, an key-value map object, or any iterable object.
// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class const meta = 'Content-Type': 'text/xml' 'Breaking-Bad': '<3';const headers = meta; // The above is equivalent toconst meta = 'Content-Type' 'text/xml' 'Breaking-Bad' '<3' ;const headers = meta; // You can in fact use any iterable objects, like a Map or even another Headersconst meta = ;meta;meta;const headers = meta;const copyOfHeaders = headers;
Interface: Body
Body
is an abstract interface with methods that are applicable to both Request
and Response
classes.
The following methods are not yet implemented in node-fetch at this moment:
formData()
body.body
(deviation from spec)
- Node.js
Readable
stream
The data encapsulated in the Body
object. Note that while the Fetch Standard requires the property to always be a WHATWG ReadableStream
, in node-fetch it is a Node.js Readable
stream.
body.bodyUsed
(spec-compliant)
Boolean
A boolean property for if this body has been consumed. Per spec, a consumed body cannot be used again.
body.arrayBuffer()
body.blob()
body.json()
body.text()
(spec-compliant)
- Returns:
Promise
Consume the body and return a promise that will resolve to one of these formats.
body.buffer()
(node-fetch extension)
- Returns:
Promise<Buffer>
Consume the body and return a promise that will resolve to a Buffer.
body.textConverted()
(node-fetch extension)
- Returns:
Promise<String>
Identical to body.text()
, except instead of always converting to UTF-8, encoding sniffing will be performed and text converted to UTF-8, if possible.
Class: FetchError
(node-fetch extension)
An operational error in the fetching process. See ERROR-HANDLING.md for more info.
License
MIT
Acknowledgement
Thanks to github/fetch for providing a solid implementation reference.