Step 3 - Creating a module bundler with Hot Module Replacement

index.js

// response with a JSONP callback function which does hot module replacement
app.get('/hot-update', function(req, res){
  var moduleId = req.query.id;
  // wrap the module code around JSONP callback function
  var hotUpdateScriptTxt = 'hotUpdate({ "' + moduleId + '":[function(require,module,exports){';
  // find the updated module in moduleDepsJSON (output from module-deps)
  var updatedModule = moduleDepsJSON.filter(function(dep) {
    return dep.id === moduleId;
  })[0];
  // append source of the updated module to the hot update script
  hotUpdateScriptTxt +=  updatedModule.source;
  // finish up hotUpdateScriptTxt
  hotUpdateScriptTxt +=  '},';
  // append dependencies
  hotUpdateScriptTxt +=  JSON.stringify(updatedModule.deps);
  hotUpdateScriptTxt += ']});';
  // send the update script
  res.send(hotUpdateScriptTxt);
});