fb-flo

fb-flo is a Chrome extension that lets you modify running apps without reloading. It's easy to integrate with your build system, dev environment, and can be used with your favorite editor.

Usage

fb-flo is made up of a server and client component. This will guide through configuring your server for your project and installing the Chrome extension.

1. Configure fb-flo server

$ npm install fb-flo

fb-flo exports a single fb-flo function to start the server. Here is an example where you have your source JavaScript and CSS files in the root directory and your build step involves bundling both into a respective bundle.js, bundle.css.

var flo = require('fb-flo'),
    path = require('path');

var server = flo(
  sourceDirToWatch,
  {
    port: 8888,
    host: 'localhost',
    verbose: false,
    glob: [
       // All JS files in `sourceDirToWatch` and subdirectories
      '**/*.js',
       // All CSS files in `sourceDirToWatch` and subdirectories
      '**/*.css'
    ]
  },
  function resolver(filepath, callback) {
    // 1. Call into your compiler / bundler.
    // 2. Assuming that `bundle.js` is your output file, update `bundle.js`
    //    and `bundle.css` when a JS or CSS file changes.
    callback({
      resourceURL: 'bundle.js' + path.extname(filepath),
      contents: fs.readFileSync(filepath)
    });
  }
);

flo takes the following arguments.

• sourceDirToWatch: absolute or relative path to the directory to watch that contains the source code that will be built.
• options hash of options:
  • port port to start the server on (defaults to 8888).
  • host to listen on.
  • verbose true or false value indicating if flo should be noisy.
  • glob a glob string or array of globs to match against the files to watch.
• resolver a function to map between files and resources.

The resolver callback is called with two arguments:

• filepath path to the file that changed relative to the watched directory.
• callback called to update a resource file in the browser. Should be called with an object with the following properties:
  • resourceURL used as an the resource identifier in the browser.
  • contents the updated code.
  • reload (optional) forces a full page reload. Use this if you're sure the changed code cannot be hotswapped.
  • match (optional, defaults to: indexOf) identifies the matching function to be performed on the resource URL in the browser. Could be one of the following:
    • "equal" test the updated resource resourceURL against existing browser resources using an equality check.
    • "indexOf" use String.prototype.indexOf check
    • /regexp/ a regexp object to exec.

2. Install the Chrome Extension

Grab the fb-flo Chrome extension. This will add a new tab in your Chrome DevTools called 'fb-flo'.

3. Activate fb-flo

To activate fb-flo from the browser:

• Open Chrome DevTools.
• Click on the new 'fb-flo' pane.
• Click on 'Activate for this site'

See screenshot:

Example

Say you have a Makefile program that builds your JavaScript and CSS into build/build.js and build/build.css respectively, this how you'd configure your fb-flo server:

var flo = require('fb-flo');
var fs = require('fs');
var exec = require('child_process').exec;

var server = flo('./lib/', {
  port: 8888,
  dir: './lib/',
  glob: ['./lib/**/*.js', './lib/**/*.css']
}, resolver);

server.once('ready', function() {
  console.log('Ready!');
});

function resolver(filepath, callback) {
    exec('make', function (err) {
      if (err) throw err;
      if (filepath.match(/\.js$/)) {
        callback({
          resourceURL: 'build/build.js',
          contents: fs.readFileSync('build/build.js').toString()
        })
      } else {
        callback({
          resourceURL: 'build/build.css',
          contents: fs.readFileSync('build/build.css').toString()
        })
      }
    });
}