A JavaScript library for efficient data fetching
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Build Status Coverage Status


2.0 is the current stable Falcor release. 0.x and 1.x users are welcome to upgrade.


Issues we're tracking as part of our roadmap are tagged with the roadmap label. They are split into enhancement, stability, performance, tooling, infrastructure and documentation categories, with near, medium and longer term labels to convey a broader sense of the order in which we plan to approach them.

Getting Started

You can check out a working example server for Netflix-like application right now. Alternately, you can go through this barebones tutorial in which we use the Falcor Router to create a Virtual JSON resource. In this tutorial we will use Falcor's express middleware to serve the Virtual JSON resource on an application server at the URL /model.json. We will also host a static web page on the same server which retrieves data from the Virtual JSON resource.

Creating a Virtual JSON Resource

In this example we will use the falcor Router to build a Virtual JSON resource on an app server and host it at /model.json. The JSON resource will contain the following contents:

  "greeting": "Hello World"

Normally, Routers retrieve the data for their Virtual JSON resource from backend datastores or other web services on-demand. However, in this simple tutorial, the Router will simply return static data for a single key.

First we create a folder for our application server.

$ mkdir falcor-app-server
$ cd falcor-app-server
$ npm init

Now we install the falcor Router.

$ npm install falcor-router --save

Then install express and falcor-express. Support for restify is also available, as is support for hapi via a third-party implementation.

$ npm install express --save
$ npm install falcor-express --save

Now we create an index.js file with the following contents:

// index.js
const falcorExpress = require('falcor-express');
const Router = require('falcor-router');

const express = require('express');
const app = express();

app.use('/model.json', falcorExpress.dataSourceRoute(function (req, res) {
  // create a Virtual JSON resource with single key ('greeting')
  return new Router([
      // match a request for the key 'greeting'
      route: 'greeting',
      // respond with a PathValue with the value of 'Hello World.'
      get: () => ({path: ['greeting'], value: 'Hello World'})

// serve static files from current directory
app.use(express.static(__dirname + '/'));


Now we run the server, which will listen on port 3000 for requests for /model.json.

$ node index.js

Retrieving Data from the Virtual JSON resource

Now that we've built a simple virtual JSON document with a single read-only key greeting, we will create a test web page and retrieve this key from the server.

Create an index.html file with the following contents:

<!-- index.html -->
    <!-- Do _not_  rely on this URL in production. Use only during development.  -->
    <script src="https://netflix.github.io/falcor/build/falcor.browser.js"></script>
    <!-- For production use. -->
    <!-- <script src="https://cdn.jsdelivr.net/falcor/{VERSION}/falcor.browser.min.js"></script> -->
      var model = falcor({source: new falcor.HttpDataSource('/model.json') });

      // retrieve the "greeting" key from the root of the Virtual JSON resource
        then(function(response) {

Now visit http://localhost:3000/index.html and you should see the message retrieved from the server:

Hello World

Steps to publish new version

  • Make pull request with feature/bug fix and tests
  • Merge pull request into master after code review and passing Travis CI checks
  • Run git checkout master to open master branch locally
  • Run git pull to merge latest code, including built dist/ and docs/ by Travis
  • Update CHANGELOG with features/bug fixes to be released in the new version
  • Run npm run prepare to build dist/ locally
  • Ensure the built files are not different from those built by Travis CI, hence creating no change to commit
  • Run npm version patch (or minor, major, etc) to create a new git commit and tag
  • Run git push origin master && git push --tags to push code and tags to github
  • Run npm publish to publish the latest version to NPM

Additional Resources