React-flavored universal XHR

Usage no npm install needed!

<script type="module">
  import reactXhr from '';



The problem

  • Data fetching for universal JS apps is hard. If you do any XHRs their data isn't present in the server-rendered markup.
  • Often you will want to send down the initial state of the app along with the webpage that bootstraps it.

What this does not solve

  • The Relay "n+1 queries problem". It's possible for you to stumble into really inefficient data fetching patterns with this. You should build some sort of batching abstraction on top of this.
  • Client-side mutations (use Flux + this)

How to use it

Declaratively specify your XHRs:

var React = require('react');
var ReactXhr = require('react-xhr');

var MyComponent = React.createClass({
  mixins: [ReactXhr.Mixin],

  getXhrs: function() {
    return {
      userInfo: {
        url: '/user/' + this.props.username,
        method: 'get',

  render: function() {
    return <div>User info: {this.state.xhrs.userInfo.body}</div>;

this.state.xhrs.X has the following properties:

  • loading: true or false if there's a pending request
  • err: any error object associated with the most recent request
  • body: parsed JSON response returned from the server, empty object if no response yet.

This in and of itself is pretty great, but you can render it server-side if you provide your own function to resolve the fetching:

// On the server

function mockXhrs(xhrs, cb) {
  // Mock backend call
  var response = {};
  for (var xhrId in xhrs) {
    var xhr = xhrs[xhrId];
    if (xhr.url.indexOf('/user/') === 0) {
      response[xhrId] = {username: xhr.url.slice('/user/'.length), isCool: true};

  <MyComponent username="floydophone" />,
  function(err, result) {

Now that you have the markup and data that you need to preload on the client, you can render on the client easily:

// On the client

ReactXhr.render(<MyComponent username="floydophone" />, preloadedData);

Advanced features

You can do other types of requests, not just xhrs. getXhrs() just returns a description of what to fetch. You can plug in your own if you want to do fetching via websocket, batched fetching, etc.

// On the client
ReactXhr.overridePerformXhr(function(xhr, cb) {
  // Read properties off of xhr (as returned from getXhrs()) and call cb(err, body)
  // with the results