iD/development_server.js

var rollup = require( 'rollup' );
var nodeResolve = require('rollup-plugin-node-resolve');
var commonjs = require('rollup-plugin-commonjs');
var json = require('rollup-plugin-json');
var http = require('http');
var gaze = require('gaze');
var ecstatic = require('ecstatic');

var cache;
var building = false;

function build() {
  if (building) return;
  building = true;
  console.log('Rebuilding');
  console.time('Rebuilt');
  rollup.rollup({
    entry: './modules/id.js',
    cache: cache,
    plugins: [
        nodeResolve({ jsnext: true, main: true, browser: false }),
        commonjs(),
        json()
    ]
  }).then(function (bundle) {
    console.timeEnd('Rebuilt');
    cache = bundle;
    bundle.write({
      format: 'iife',
      dest: 'dist/iD.js',
      sourceMap: true
    });
    building = false;
  });
}

if (process.argv[2] === 'develop') {
    build();
    gaze('modules/**.js', function(err, watcher) {
        watcher.on('all', function() {
            build();
        });
    });
    http.createServer(
      ecstatic({ root: __dirname })
    ).listen(8080);
    console.log('Listening on :8080');
} else {
    build();
}