node-fetch-polyfill

node-fetch

A light-weight module that brings window.fetch to Node.js

Motivation

I really like the notion of Matt Andrews' isomorphic-fetch: it bridges the API gap between client-side and server-side http requests, so developers have less to worry about.

Instead of implementing XMLHttpRequest in node to run browser-specific fetch polyfill, why not go from node's http to fetch API directly? Node has native stream support, browserify build targets (browsers) don't, so underneath they are going to be vastly different anyway.

Hence node-fetch, minimal code for a window.fetch compatible API on Node.js runtime.

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 WhatWG ReadableStream for streaming bodies, on both request and response.
• Useful extensions such as timeout, redirect limit, response size limit, explicit reject errors.

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-polyfill --save

Usage

var fetch = require('node-fetch-polyfill');
 
// If you are not on node v0.12, 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);
    });
 
// 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)
 
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 0.11+, 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. 0 to disable (os limit still applies), timeout reset on redirect
    , 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.