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https://github.com/avaer/window-fetch

Browser window.fetch polyfill
https://github.com/avaer/window-fetch

Last synced: 15 days ago
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Browser window.fetch polyfill

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node-fetch

==========



[![npm version][npm-image]][npm-url]

[![build status][travis-image]][travis-url]

[![coverage status][codecov-image]][codecov-url]



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](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) 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 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()` and `res.json()`) to UTF-8 automatically.

- Useful extensions such as timeout, redirect limit, response size limit, [explicit errors](https://github.com/bitinn/node-fetch/blob/master/ERROR-HANDLING.md) for troubleshooting.



## Difference from client-side fetch



- See [Known Differences](https://github.com/bitinn/node-fetch/blob/master/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!



## Install



Stable release (`1.x`)



```sh

$ npm install node-fetch --save

```



Next release (`2.x`), currently in alpha



```sh

$ npm install node-fetch@next --save

```



## Usage



Note that documentation below is up-to-date with `2.x` releases, [see `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](https://github.com/bitinn/node-fetch/blob/master/UPGRADE-GUIDE.md) if you want to find out the difference.



```javascript

import fetch from 'node-fetch';

// 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



fetch('https://github.com/')

	.then(res => res.text())

	.then(body => console.log(body));



// json



fetch('https://api.github.com/users/github')

	.then(res => res.json())

	.then(json => console.log(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



fetch('http://domain.invalid/')

	.catch(err => console.error(err));



// stream

// the node.js way is to use stream when possible



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 that buffer() is a node-fetch only API



import fileType from 'file-type';



fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')

	.then(res => res.buffer())

	.then(buffer => fileType(buffer))

	.then(type => { /* ... */ });



// meta



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'));

	});



// post



fetch('http://httpbin.org/post', { method: 'POST', body: 'a=1' })

	.then(res => res.json())

	.then(json => console.log(json));



// post with stream from file



import { createReadStream } from 'fs';



const stream = createReadStream('input.txt');

fetch('http://httpbin.org/post', { method: 'POST', body: stream })

	.then(res => res.json())

	.then(json => console.log(json));



// post with JSON



var body = { a: 1 };

fetch('http://httpbin.org/post', { 

	method: 'POST',

	body:    JSON.stringify(body),

	headers: { 'Content-Type': 'application/json' },

})

	.then(res => res.json())

	.then(json => console.log(json));



// post form parameters (x-www-form-urlencoded)



import { URLSearchParams } from 'url';



const params = new URLSearchParams();

params.append('a', 1);

fetch('http://httpbin.org/post', { method: 'POST', body: params })

	.then(res => res.json())

	.then(json => console.log(json));



// post with form-data (detect multipart)



import FormData from 'form-data';



const form = new FormData();

form.append('a', 1);

fetch('http://httpbin.org/post', { method: 'POST', body: form })

	.then(res => res.json())

	.then(json => console.log(json));



// post with form-data (custom headers)

// note that getHeaders() is non-standard API



import FormData from 'form-data';



const form = new FormData();

form.append('a', 1);

fetch('http://httpbin.org/post', { method: 'POST', body: form, headers: form.getHeaders() })

	.then(res => res.json())

	.then(json => console.log(json));



// node 7+ with async function



(async function () {

	const res = await fetch('https://api.github.com/users/github');

	const json = await res.json();

	console.log(json);

})();

```



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: Promise<[Response](#class-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.



```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



	// 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](#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])



*(spec-compliant)*



- `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.





### 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`

- `redirected`

- `trailer`



#### new Response([body[, options]])



*(spec-compliant)*



- `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



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][whatwg-fetch] are implemented.



#### new Headers([init])



*(spec-compliant)*



- `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);

```





### 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][node-readable]



The data 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



*(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](https://github.com/github/fetch) for providing a solid implementation reference.



[npm-image]: https://img.shields.io/npm/v/node-fetch.svg?style=flat-square

[npm-url]: https://www.npmjs.com/package/node-fetch

[travis-image]: https://img.shields.io/travis/bitinn/node-fetch.svg?style=flat-square

[travis-url]: https://travis-ci.org/bitinn/node-fetch

[codecov-image]: https://img.shields.io/codecov/c/github/bitinn/node-fetch.svg?style=flat-square

[codecov-url]: https://codecov.io/gh/bitinn/node-fetch

[ERROR-HANDLING.md]: https://github.com/bitinn/node-fetch/blob/master/ERROR-HANDLING.md

[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