CORE_V5 // node-fetch-npm

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node-fetch-npm
==============

[![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

`node-fetch-npm` is a fork of [`node-fetch`](https://npm.im/node-fetch) used in
npm itself, through [`make-fetch-happen`](https://npm.im/make-fetch-happen). It
has more regular releases and accepts some patches that would not fit with
`node-fetch`'s own design goals (such as picking a specific cookie library,
removing `babel` dependency altogether, etc).

This library is *not a replacement* for `node-fetch`, nor does it intend to
supplant it. It's purely a fork maintained for the sake of easier patching of
specific needs that it wouldn't be fair to shove down the main project's throat.
This project will still send patches for shared bugs over and hopefully help
improve its "parent".

## 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][] for troubleshooting.

## Difference from client-side fetch

- See [Known Differences](https://github.com/npm/node-fetch-npm/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

```sh
$ npm install node-fetch-npm --save
```

## Usage

```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 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/npm/node-fetch-npm/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 `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.

<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

// The following properties are node-fetch-npm 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-npm/1.0 (+https://github.com/npm/node-fetch-npm)`

<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-npm 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.

<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-npm 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.

<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])

*(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);
```

<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-npm 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-npm 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: <code>Promise</code>

Consume the body and return a promise that will resolve to one of these formats.

#### body.buffer()

*(node-fetch-npm extension)*

* Returns: <code>Promise&lt;Buffer&gt;</code>

Consume the body and return a promise that will resolve to a Buffer.

#### body.textConverted()

*(node-fetch-npm extension)*

* 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.

<a id="class-fetcherror"></a>
### Class: FetchError

*(node-fetch-npm 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-npm.svg?style=flat-square
[npm-url]: https://www.npmjs.com/package/node-fetch-npm
[travis-image]: https://img.shields.io/travis/npm/node-fetch-npm.svg?style=flat-square
[travis-url]: https://travis-ci.org/npm/node-fetch-npm
[codecov-image]: https://img.shields.io/codecov/c/github/npm/node-fetch-npm.svg?style=flat-square
[codecov-url]: https://codecov.io/gh/npm/node-fetch-npm
[ERROR-HANDLING.md]: https://github.com/npm/node-fetch-npm/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

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