newsroom/node_modules/node-fetch

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() 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 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

npm install node-fetch --save

Usage

var fetch = require('node-fetch');

// if you are on node v0.10, set a Promise library first, eg.
// fetch.Promise = require('bluebird');

// plain text or html

fetch('https://github.com/')
	.then(function(res) {
		return res.text();
	}).then(function(body) {
		console.log(body);
	});

// json

fetch('https://api.github.com/users/github')
	.then(function(res) {
		return res.json();
	}).then(function(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(function(err) {
		console.log(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(function(res) {
		var 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

var fileType = require('file-type');
fetch('https://assets-cdn.github.com/images/modules/logos_page/Octocat.png')
	.then(function(res) {
		return res.buffer();
	}).then(function(buffer) {
		fileType(buffer);
	});

// meta

fetch('https://github.com/')
	.then(function(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(function(res) {
		return res.json();
	}).then(function(json) {
		console.log(json);
	});

// post with stream from resumer

var resumer = require('resumer');
var stream = resumer().queue('a=1').end();
fetch('http://httpbin.org/post', { method: 'POST', body: stream })
	.then(function(res) {
		return res.json();
	}).then(function(json) {
		console.log(json);
	});

// post with form-data (detect multipart)

var FormData = require('form-data');
var form = new FormData();
form.append('a', 1);
fetch('http://httpbin.org/post', { method: 'POST', body: form })
	.then(function(res) {
		return res.json();
	}).then(function(json) {
		console.log(json);
	});

// post with form-data (custom headers)
// note that getHeaders() is non-standard API

var FormData = require('form-data');
var form = new FormData();
form.append('a', 1);
fetch('http://httpbin.org/post', { method: 'POST', body: form, headers: form.getHeaders() })
	.then(function(res) {
		return res.json();
	}).then(function(json) {
		console.log(json);
	});

// node 0.12+, yield with co

var co = require('co');
co(function *() {
	var res = yield fetch('https://api.github.com/users/github');
	var json = yield res.json();
	console.log(res);
});

See test cases for more examples.

API

fetch(url, options)

Returns a Promise

Url

Should be an absolute url, eg http://example.com/

Options

default values are shown, note that only method, headers, redirect and body are allowed in window.fetch, others are node.js extensions.

{
	method: 'GET'
	, headers: {}        // request header. format {a:'1'} or {b:['1','2','3']}
	, redirect: 'follow' // set to `manual` to extract redirect headers, `error` to reject redirect
	, 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
	, body: empty        // request body. can be a string, buffer, readable stream
	, agent: null        // http.Agent instance, allows custom proxy, certificate etc.
}

License

MIT

Acknowledgement

Thanks to github/fetch for providing a solid implementation reference.