Step 3a - Creating a module bundler with Hot Module Replacement

hotUpdate.js

// this function will be added to the final bundle produced by
// browser-pack using 'prelude' option
this.hotUpdate = function(updatedModules) {
        for (var id in updatedModules) {
            if(Object.prototype.hasOwnProperty.call(updatedModules, id)) {
                // clear module definition from cache
                delete cache[id];
                // replace existing module definition from module map
                modules[id] = updatedModules[id];
                // Update module - 'newRequire' is from browser-pack
                newRequire(id);
                console.log('Update applied.');
                // call entry point modules to bootstrap
                for(var i=0;i<entry.length;i++) {
                    // delete existing entry point module in cache
                    // so that it is reinitialized
                    delete cache[entry[i]];
                    // call entry point module which will run
                    // with new updates in cache
                    newRequire(entry[i]);
                }
            }
        }
    };