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README.md (19782B)

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 node-fetch
 ==========
 
 [![npm version][npm-image]][npm-url]
 [![build status][travis-image]][travis-url]
 [![coverage status][codecov-image]][codecov-url]
 [![install size][install-size-image]][install-size-url]
 [![Discord][discord-image]][discord-url]
 
 A light-weight module that brings `window.fetch` to Node.js
 
 (We are looking for [v2 maintainers and collaborators](https://github.com/bitinn/node-fetch/issues/567))
 
 [![Backers][opencollective-image]][opencollective-url]
 
 <!-- TOC -->
 
 - [Motivation](#motivation)
 - [Features](#features)
 - [Difference from client-side fetch](#difference-from-client-side-fetch)
 - [Installation](#installation)
 - [Loading and configuring the module](#loading-and-configuring-the-module)
 - [Common Usage](#common-usage)
     - [Plain text or HTML](#plain-text-or-html)
     - [JSON](#json)
     - [Simple Post](#simple-post)
     - [Post with JSON](#post-with-json)
     - [Post with form parameters](#post-with-form-parameters)
     - [Handling exceptions](#handling-exceptions)
     - [Handling client and server errors](#handling-client-and-server-errors)
 - [Advanced Usage](#advanced-usage)
     - [Streams](#streams)
     - [Buffer](#buffer)
     - [Accessing Headers and other Meta data](#accessing-headers-and-other-meta-data)
     - [Extract Set-Cookie Header](#extract-set-cookie-header)
     - [Post data using a file stream](#post-data-using-a-file-stream)
     - [Post with form-data (detect multipart)](#post-with-form-data-detect-multipart)
     - [Request cancellation with AbortSignal](#request-cancellation-with-abortsignal)
 - [API](#api)
     - [fetch(url[, options])](#fetchurl-options)
     - [Options](#options)
     - [Class: Request](#class-request)
     - [Class: Response](#class-response)
     - [Class: Headers](#class-headers)
     - [Interface: Body](#interface-body)
     - [Class: FetchError](#class-fetcherror)
 - [License](#license)
 - [Acknowledgement](#acknowledgement)
 
 <!-- /TOC -->
 
 ## Motivation
 
 Instead of implementing `XMLHttpRequest` in Node.js to run browser-specific [Fetch polyfill](https://github.com/github/fetch), 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](https://github.com/matthew-andrews/isomorphic-fetch) or Leonardo Quixada's [cross-fetch](https://github.com/lquixada/cross-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][whatwg-fetch] and [stream spec](https://streams.spec.whatwg.org/) implementation details, document known differences.
 - Use native promise but allow substituting it with [insert your favorite promise library].
 - Use native Node streams for body on both request and response.
 - Decode content encoding (gzip/deflate) properly and convert string output (such as `res.text()` and `res.json()`) to UTF-8 automatically.
 - Useful extensions such as timeout, redirect limit, response size limit, [explicit errors](ERROR-HANDLING.md) for troubleshooting.
 
 ## Difference from client-side fetch
 
 - See [Known Differences](LIMITS.md) 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!
 
 ## Installation
 
 Current stable release (`2.x`)
 
 ```sh
 $ npm install node-fetch
 ```
 
 ## Loading and configuring the module
 We suggest you load the module via `require` until the stabilization of ES modules in node:
 ```js
 const fetch = require('node-fetch');
 ```
 
 If you are using a Promise library other than native, set it through `fetch.Promise`:
 ```js
 const Bluebird = require('bluebird');
 
 fetch.Promise = Bluebird;
 ```
 
 ## Common Usage
 
 NOTE: The documentation below is up-to-date with `2.x` releases; see the [`1.x` readme](https://github.com/bitinn/node-fetch/blob/1.x/README.md), [changelog](https://github.com/bitinn/node-fetch/blob/1.x/CHANGELOG.md) and [2.x upgrade guide](UPGRADE-GUIDE.md) for the differences.
 
 #### Plain text or HTML
 ```js
 fetch('https://github.com/')
     .then(res => res.text())
     .then(body => console.log(body));
 ```
 
 #### JSON
 
 ```js
 
 fetch('https://api.github.com/users/github')
     .then(res => res.json())
     .then(json => console.log(json));
 ```
 
 #### Simple Post
 ```js
 fetch('https://httpbin.org/post', { method: 'POST', body: 'a=1' })
     .then(res => res.json()) // expecting a json response
     .then(json => console.log(json));
 ```
 
 #### Post with JSON
 
 ```js
 const body = { a: 1 };
 
 fetch('https://httpbin.org/post', {
         method: 'post',
         body:    JSON.stringify(body),
         headers: { 'Content-Type': 'application/json' },
     })
     .then(res => res.json())
     .then(json => console.log(json));
 ```
 
 #### Post with form parameters
 `URLSearchParams` is available in Node.js as of v7.5.0. See [official documentation](https://nodejs.org/api/url.html#url_class_urlsearchparams) for more usage methods.
 
 NOTE: The `Content-Type` header is only set automatically to `x-www-form-urlencoded` when an instance of `URLSearchParams` is given as such:
 
 ```js
 const { URLSearchParams } = require('url');
 
 const params = new URLSearchParams();
 params.append('a', 1);
 
 fetch('https://httpbin.org/post', { method: 'POST', body: params })
     .then(res => res.json())
     .then(json => console.log(json));
 ```
 
 #### Handling exceptions
 NOTE: 3xx-5xx responses are *NOT* exceptions and should be handled in `then()`; see the next section for more information.
 
 Adding a catch to the fetch promise chain will catch *all* exceptions, such as errors originating from node core libraries, network errors and operational errors, which are instances of FetchError. See the [error handling document](ERROR-HANDLING.md)  for more details.
 
 ```js
 fetch('https://domain.invalid/')
     .catch(err => console.error(err));
 ```
 
 #### Handling client and server errors
 It is common to create a helper function to check that the response contains no client (4xx) or server (5xx) error responses:
 
 ```js
 function checkStatus(res) {
     if (res.ok) { // res.status >= 200 && res.status < 300
         return res;
     } else {
         throw MyCustomError(res.statusText);
     }
 }
 
 fetch('https://httpbin.org/status/400')
     .then(checkStatus)
     .then(res => console.log('will not get here...'))
 ```
 
 ## Advanced Usage
 
 #### Streams
 The "Node.js way" is to use streams when possible:
 
 ```js
 fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
     .then(res => {
         const dest = fs.createWriteStream('./octocat.png');
         res.body.pipe(dest);
     });
 ```
 
 #### Buffer
 If you prefer to cache binary data in full, use buffer(). (NOTE: `buffer()` is a `node-fetch`-only API)
 
 ```js
 const fileType = require('file-type');
 
 fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
     .then(res => res.buffer())
     .then(buffer => fileType(buffer))
     .then(type => { /* ... */ });
 ```
 
 #### Accessing Headers and other Meta data
 ```js
 fetch('https://github.com/')
     .then(res => {
         console.log(res.ok);
         console.log(res.status);
         console.log(res.statusText);
         console.log(res.headers.raw());
         console.log(res.headers.get('content-type'));
     });
 ```
 
 #### Extract Set-Cookie Header
 
 Unlike browsers, you can access raw `Set-Cookie` headers manually using `Headers.raw()`. This is a `node-fetch` only API.
 
 ```js
 fetch(url).then(res => {
     // returns an array of values, instead of a string of comma-separated values
     console.log(res.headers.raw()['set-cookie']);
 });
 ```
 
 #### Post data using a file stream
 
 ```js
 const { createReadStream } = require('fs');
 
 const stream = createReadStream('input.txt');
 
 fetch('https://httpbin.org/post', { method: 'POST', body: stream })
     .then(res => res.json())
     .then(json => console.log(json));
 ```
 
 #### Post with form-data (detect multipart)
 
 ```js
 const FormData = require('form-data');
 
 const form = new FormData();
 form.append('a', 1);
 
 fetch('https://httpbin.org/post', { method: 'POST', body: form })
     .then(res => res.json())
     .then(json => console.log(json));
 
 // OR, using custom headers
 // NOTE: getHeaders() is non-standard API
 
 const form = new FormData();
 form.append('a', 1);
 
 const options = {
     method: 'POST',
     body: form,
     headers: form.getHeaders()
 }
 
 fetch('https://httpbin.org/post', options)
     .then(res => res.json())
     .then(json => console.log(json));
 ```
 
 #### Request cancellation with AbortSignal
 
 > NOTE: You may cancel streamed requests only on Node >= v8.0.0
 
 You may cancel requests with `AbortController`. A suggested implementation is [`abort-controller`](https://www.npmjs.com/package/abort-controller).
 
 An example of timing out a request after 150ms could be achieved as the following:
 
 ```js
 import AbortController from 'abort-controller';
 
 const controller = new AbortController();
 const timeout = setTimeout(
   () => { controller.abort(); },
   150,
 );
 
 fetch(url, { signal: controller.signal })
   .then(res => res.json())
   .then(
     data => {
       useData(data)
     },
     err => {
       if (err.name === 'AbortError') {
         // request was aborted
       }
     },
   )
   .finally(() => {
     clearTimeout(timeout);
   });
 ```
 
 See [test cases](https://github.com/bitinn/node-fetch/blob/master/test/test.js) for more examples.
 
 
 ## API
 
 ### fetch(url[, options])
 
 - `url` A string representing the URL for fetching
 - `options` [Options](#fetch-options) for the HTTP(S) request
 - Returns: <code>Promise&lt;[Response](#class-response)&gt;</code>
 
 Perform an HTTP(S) fetch.
 
 `url` should be an absolute url, such as `https://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`.
 
 <a id="fetch-options"></a>
 ### Options
 
 The default values are shown after each option key.
 
 ```js
 {
     // 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
     signal: null,       // pass an instance of AbortSignal to optionally abort requests
 
     // 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). Signal is recommended instead.
     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 or function that returns an instance (see below)
 }
 ```
 
 ##### 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)_
 `Transfer-Encoding` | `chunked` _(when `req.body` is a stream)_
 `User-Agent`        | `node-fetch/1.0 (+https://github.com/bitinn/node-fetch)`
 
 Note: when `body` is a `Stream`, `Content-Length` is not set automatically.
 
 ##### Custom Agent
 
 The `agent` option allows you to specify networking related options which are out of the scope of Fetch, including and not limited to the following:
 
 - Support self-signed certificate
 - Use only IPv4 or IPv6
 - Custom DNS Lookup
 
 See [`http.Agent`](https://nodejs.org/api/http.html#http_new_agent_options) for more information.
 
 In addition, the `agent` option accepts a function that returns `http`(s)`.Agent` instance given current [URL](https://nodejs.org/api/url.html), this is useful during a redirection chain across HTTP and HTTPS protocol.
 
 ```js
 const httpAgent = new http.Agent({
     keepAlive: true
 });
 const httpsAgent = new https.Agent({
     keepAlive: true
 });
 
 const options = {
     agent: function (_parsedURL) {
         if (_parsedURL.protocol == 'http:') {
             return httpAgent;
         } else {
             return httpsAgent;
         }
     }
 }
 ```
 
 <a id="class-request"></a>
 ### Class: Request
 
 An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the [Body](#iface-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](#fetch-options) for exact meaning of these extensions.
 
 #### new Request(input[, options])
 
 <small>*(spec-compliant)*</small>
 
 - `input` A string representing a URL, or another `Request` (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](https://developer.mozilla.org/en-US/docs/Web/API/Request/Request).
 
 In most cases, directly `fetch(url, options)` is simpler than creating a `Request` object.
 
 <a id="class-response"></a>
 ### Class: Response
 
 An HTTP(S) response. This class implements the [Body](#iface-body) interface.
 
 The following properties are not implemented in node-fetch at this moment:
 
 - `Response.error()`
 - `Response.redirect()`
 - `type`
 - `trailer`
 
 #### new Response([body[, options]])
 
 <small>*(spec-compliant)*</small>
 
 - `body` A `String` or [`Readable` stream][node-readable]
 - `options` A [`ResponseInit`][response-init] options dictionary
 
 Constructs a new `Response` object. The constructor is identical to that in the [browser](https://developer.mozilla.org/en-US/docs/Web/API/Response/Response).
 
 Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a `Response` directly.
 
 #### response.ok
 
 <small>*(spec-compliant)*</small>
 
 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.
 
 #### response.redirected
 
 <small>*(spec-compliant)*</small>
 
 Convenience property representing if the request has been redirected at least once. Will evaluate to true if the internal redirect counter is greater than 0.
 
 <a id="class-headers"></a>
 ### Class: Headers
 
 This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the [Fetch Standard][whatwg-fetch] are implemented.
 
 #### new Headers([init])
 
 <small>*(spec-compliant)*</small>
 
 - `init` Optional argument to pre-fill the `Headers` object
 
 Construct a new `Headers` object. `init` can be either `null`, a `Headers` object, an key-value map object or any iterable object.
 
 ```js
 // Example adapted from https://fetch.spec.whatwg.org/#example-headers-class
 
 const meta = {
   'Content-Type': 'text/xml',
   'Breaking-Bad': '<3'
 };
 const headers = new Headers(meta);
 
 // The above is equivalent to
 const meta = [
   [ 'Content-Type', 'text/xml' ],
   [ 'Breaking-Bad', '<3' ]
 ];
 const headers = new Headers(meta);
 
 // You can in fact use any iterable objects, like a Map or even another Headers
 const meta = new Map();
 meta.set('Content-Type', 'text/xml');
 meta.set('Breaking-Bad', '<3');
 const headers = new Headers(meta);
 const copyOfHeaders = new Headers(headers);
 ```
 
 <a id="iface-body"></a>
 ### 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
 
 <small>*(deviation from spec)*</small>
 
 * Node.js [`Readable` stream][node-readable]
 
 Data are encapsulated in the `Body` object. Note that while the [Fetch Standard][whatwg-fetch] requires the property to always be a WHATWG `ReadableStream`, in node-fetch it is a Node.js [`Readable` stream][node-readable].
 
 #### body.bodyUsed
 
 <small>*(spec-compliant)*</small>
 
 * `Boolean`
 
 A boolean property for if this body has been consumed. Per the specs, a consumed body cannot be used again.
 
 #### body.arrayBuffer()
 #### body.blob()
 #### body.json()
 #### body.text()
 
 <small>*(spec-compliant)*</small>
 
 * Returns: <code>Promise</code>
 
 Consume the body and return a promise that will resolve to one of these formats.
 
 #### body.buffer()
 
 <small>*(node-fetch extension)*</small>
 
 * Returns: <code>Promise&lt;Buffer&gt;</code>
 
 Consume the body and return a promise that will resolve to a Buffer.
 
 #### body.textConverted()
 
 <small>*(node-fetch extension)*</small>
 
 * Returns: <code>Promise&lt;String&gt;</code>
 
 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.
 
 (This API requires an optional dependency of the npm package [encoding](https://www.npmjs.com/package/encoding), which you need to install manually. `webpack` users may see [a warning message](https://github.com/bitinn/node-fetch/issues/412#issuecomment-379007792) due to this optional dependency.)
 
 <a id="class-fetcherror"></a>
 ### Class: FetchError
 
 <small>*(node-fetch extension)*</small>
 
 An operational error in the fetching process. See [ERROR-HANDLING.md][] for more info.
 
 <a id="class-aborterror"></a>
 ### Class: AbortError
 
 <small>*(node-fetch extension)*</small>
 
 An Error thrown when the request is aborted in response to an `AbortSignal`'s `abort` event. It has a `name` property of `AbortError`. See [ERROR-HANDLING.MD][] for more info.
 
 ## Acknowledgement
 
 Thanks to [github/fetch](https://github.com/github/fetch) for providing a solid implementation reference.
 
 `node-fetch` v1 was maintained by [@bitinn](https://github.com/bitinn); v2 was maintained by [@TimothyGu](https://github.com/timothygu), [@bitinn](https://github.com/bitinn) and [@jimmywarting](https://github.com/jimmywarting); v2 readme is written by [@jkantr](https://github.com/jkantr).
 
 ## License
 
 MIT
 
 [npm-image]: https://flat.badgen.net/npm/v/node-fetch
 [npm-url]: https://www.npmjs.com/package/node-fetch
 [travis-image]: https://flat.badgen.net/travis/bitinn/node-fetch
 [travis-url]: https://travis-ci.org/bitinn/node-fetch
 [codecov-image]: https://flat.badgen.net/codecov/c/github/bitinn/node-fetch/master
 [codecov-url]: https://codecov.io/gh/bitinn/node-fetch
 [install-size-image]: https://flat.badgen.net/packagephobia/install/node-fetch
 [install-size-url]: https://packagephobia.now.sh/result?p=node-fetch
 [discord-image]: https://img.shields.io/discord/619915844268326952?color=%237289DA&label=Discord&style=flat-square
 [discord-url]: https://discord.gg/Zxbndcm
 [opencollective-image]: https://opencollective.com/node-fetch/backers.svg
 [opencollective-url]: https://opencollective.com/node-fetch
 [whatwg-fetch]: https://fetch.spec.whatwg.org/
 [response-init]: https://fetch.spec.whatwg.org/#responseinit
 [node-readable]: https://nodejs.org/api/stream.html#stream_readable_streams
 [mdn-headers]: https://developer.mozilla.org/en-US/docs/Web/API/Headers
 [LIMITS.md]: https://github.com/bitinn/node-fetch/blob/master/LIMITS.md
 [ERROR-HANDLING.md]: https://github.com/bitinn/node-fetch/blob/master/ERROR-HANDLING.md
 [UPGRADE-GUIDE.md]: https://github.com/bitinn/node-fetch/blob/master/UPGRADE-GUIDE.md