This example show how to use Code Splitting with the ES6 module syntax.

The standard import is sync.

System.import(module: string) -> Promise can be used to load modules on demand. This acts as split point for webpack and creates a chunk.

Providing dynamic expressions to System.import is possible. The same limits as with dynamic expressions in require calls apply here. Each possible module creates an additional chunk. In this example System.import("c/" + name) creates two additional chunks (one for each file in node_modules/c/). This is called "async context".

example.js

import a from "a";

System.import("b").then(function(b) {
	console.log("b loaded", b);
})

function loadC(name) {
	return System.import("c/" + name)
}

Promise.all([loadC("1"), loadC("2")]).then(function(arr) {
	console.log("c/1 and c/2 loaded", arr);
});

js/output.js

`/******/ (function(modules) { /* webpackBootstrap */ })`

``` javascript /******/ (function(modules) { // webpackBootstrap /******/ // install a JSONP callback for chunk loading /******/ var parentJsonpFunction = window["webpackJsonp"]; /******/ window["webpackJsonp"] = function webpackJsonpCallback(chunkIds, moreModules, executeModules) { /******/ // add "moreModules" to the modules object, /******/ // then flag all "chunkIds" as loaded and fire callback /******/ var moduleId, chunkId, i = 0, resolves = [], result; /******/ for(;i < chunkIds.length; i++) { /******/ chunkId = chunkIds[i]; /******/ if(installedChunks[chunkId]) /******/ resolves.push(installedChunks[chunkId][0]); /******/ installedChunks[chunkId] = 0; /******/ } /******/ for(moduleId in moreModules) { /******/ if(Object.prototype.hasOwnProperty.call(moreModules, moduleId)) { /******/ modules[moduleId] = moreModules[moduleId]; /******/ } /******/ } /******/ if(parentJsonpFunction) parentJsonpFunction(chunkIds, moreModules, executeModules); /******/ while(resolves.length) /******/ resolves.shift()();

/******/ };

// // The module cache // var installedModules = {};

// // objects to store loaded and loading chunks // var installedChunks = { // 3: 0 // };

// // The require function // function webpack_require(moduleId) {

// // Check if module is in cache // if(installedModules[moduleId]) /******/ return installedModules[moduleId].exports;

// // Create a new module (and put it into the cache) // var module = installedModules[moduleId] = { // i: moduleId, // l: false, // exports: {} // };

// // Execute the module function // modules[moduleId].call(module.exports, module, module.exports, webpack_require);

// // Flag the module as loaded // module.l = true;

// // Return the exports of the module // return module.exports; /******/ }

// // This file contains only the entry chunk. // // The chunk loading function for additional chunks // webpack_require.e = function requireEnsure(chunkId) { // if(installedChunks[chunkId] === 0) /******/ return Promise.resolve();

// // an Promise means "currently loading". // if(installedChunks[chunkId]) { // return installedChunks[chunkId][2]; // } // // start chunk loading // var head = document.getElementsByTagName('head')[0]; // var script = document.createElement('script'); // script.type = 'text/javascript'; // script.charset = 'utf-8'; // script.async = true; /******/ script.timeout = 120000;

// if (webpack_require.nc) { // script.setAttribute("nonce", webpack_require.nc); // } // script.src = webpack_require.p + "" + chunkId + ".output.js"; // var timeout = setTimeout(onScriptComplete, 120000); // script.onerror = script.onload = onScriptComplete; // function onScriptComplete() { // // avoid mem leaks in IE. // script.onerror = script.onload = null; // clearTimeout(timeout); // var chunk = installedChunks[chunkId]; // if(chunk !== 0) { // if(chunk) chunk[1](new Error('Loading chunk ' + chunkId + ' failed.')); // installedChunks[chunkId] = undefined; // } // };

// var promise = new Promise(function(resolve, reject) { // installedChunks[chunkId] = [resolve, reject]; // }); // installedChunks[chunkId][2] = promise;

// head.appendChild(script); // return promise; /******/ };

// // expose the modules object (webpack_modules) // webpack_require.m = modules;

// // expose the module cache // webpack_require.c = installedModules;

// // identity function for calling harmony imports with the correct context // webpack_require.i = function(value) { return value; };

// // define getter function for harmony exports // webpack_require.d = function(exports, name, getter) { // if(!webpack_require.o(exports, name)) { // Object.defineProperty(exports, name, { // configurable: false, // enumerable: true, // get: getter // }); // } // };

// // getDefaultExport function for compatibility with non-harmony modules // webpack_require.n = function(module) { // var getter = module && module.__esModule ? // function getDefault() { return module['default']; } : // function getModuleExports() { return module; }; // webpack_require.d(getter, 'a', getter); // return getter; // };

// // Object.prototype.hasOwnProperty.call // webpack_require.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };

// // webpack_public_path // webpack_require.p = "js/";

// // on error function for async loading // webpack_require.oe = function(err) { console.error(err); throw err; };

// // Load entry module and return exports // return webpack_require(webpack_require.s = 5); // }) /******************************************************************/

</details>
``` javascript
/******/ ([
/* 0 */
/* unknown exports provided */
/*!****************!*\
  !*** ./~/a.js ***!
  \****************/
/***/ function(module, exports) {

// module a

/***/ },
/* 1 */
/* unknown exports provided */
/* all exports used */
/*!****************************!*\
  !*** ./~/c async ^\.\/.*$ ***!
  \****************************/
/***/ function(module, exports, __webpack_require__) {

var map = {
	"./1": [
		2,
		1
	],
	"./1.js": [
		2,
		1
	],
	"./2": [
		3,
		0
	],
	"./2.js": [
		3,
		0
	]
};
function webpackAsyncContext(req) {
	var ids = map[req];	if(!ids)
		return Promise.reject(new Error("Cannot find module '" + req + "'."));
	return __webpack_require__.e(ids[1]).then(function() {
		return __webpack_require__(ids[0]);
	});
};
webpackAsyncContext.keys = function webpackAsyncContextKeys() {
	return Object.keys(map);
};
module.exports = webpackAsyncContext;
webpackAsyncContext.id = 1;


/***/ },
/* 2 */,
/* 3 */,
/* 4 */,
/* 5 */
/* unknown exports provided */
/* all exports used */
/*!********************!*\
  !*** ./example.js ***!
  \********************/
/***/ function(module, exports, __webpack_require__) {

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_0_a__ = __webpack_require__(/*! a */ 0);
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_0_a___default = __webpack_require__.n(__WEBPACK_IMPORTED_MODULE_0_a__);


__webpack_require__.e/* import() */(2).then(__webpack_require__.bind(null, /*! b */ 4)).then(function(b) {
	console.log("b loaded", b);
})

function loadC(name) {
	return __webpack_require__(/*! c */ 1)("./" + name)
}

Promise.all([loadC("1"), loadC("2")]).then(function(arr) {
	console.log("c/1 and c/2 loaded", arr);
});


/***/ }
/******/ ]);

Info

Uncompressed

Hash: a7c705649f12226cfe93
Version: webpack 2.2.0-rc.2
      Asset       Size  Chunks             Chunk Names
0.output.js  216 bytes       0  [emitted]  
1.output.js  216 bytes       1  [emitted]  
2.output.js  208 bytes       2  [emitted]  
  output.js    7.22 kB       3  [emitted]  main
Entrypoint main = output.js
chunk    {0} 0.output.js 13 bytes {3} [rendered]
    [3] ./~/c/2.js 13 bytes {0} [optional] [built]
        context element ./2 [1] ./~/c async ^\.\/.*$
        context element ./2.js [1] ./~/c async ^\.\/.*$
chunk    {1} 1.output.js 13 bytes {3} [rendered]
    [2] ./~/c/1.js 13 bytes {1} [optional] [built]
        context element ./1 [1] ./~/c async ^\.\/.*$
        context element ./1.js [1] ./~/c async ^\.\/.*$
chunk    {2} 2.output.js 11 bytes {3} [rendered]
    > [5] ./example.js 3:0-18
    [4] ./~/b.js 11 bytes {2} [built]
        import() b [5] ./example.js 3:0-18
chunk    {3} output.js (main) 440 bytes [entry] [rendered]
    > main [5] ./example.js 
    [0] ./~/a.js 11 bytes {3} [built]
        [no exports used]
        harmony import a [5] ./example.js 1:0-18
    [1] ./~/c async ^\.\/.*$ 160 bytes {3} [built]
        System.import context c [5] ./example.js 8:8-34
    [5] ./example.js 269 bytes {3} [built]

Minimized (uglify-js, no zip)

Hash: a7c705649f12226cfe93
Version: webpack 2.2.0-rc.2
      Asset      Size  Chunks             Chunk Names
0.output.js  38 bytes       0  [emitted]  
1.output.js  38 bytes       1  [emitted]  
2.output.js  38 bytes       2  [emitted]  
  output.js   1.92 kB       3  [emitted]  main
Entrypoint main = output.js
chunk    {0} 0.output.js 13 bytes {3} [rendered]
    [3] ./~/c/2.js 13 bytes {0} [optional] [built]
        context element ./2 [1] ./~/c async ^\.\/.*$
        context element ./2.js [1] ./~/c async ^\.\/.*$
chunk    {1} 1.output.js 13 bytes {3} [rendered]
    [2] ./~/c/1.js 13 bytes {1} [optional] [built]
        context element ./1 [1] ./~/c async ^\.\/.*$
        context element ./1.js [1] ./~/c async ^\.\/.*$
chunk    {2} 2.output.js 11 bytes {3} [rendered]
    > [5] ./example.js 3:0-18
    [4] ./~/b.js 11 bytes {2} [built]
        import() b [5] ./example.js 3:0-18
chunk    {3} output.js (main) 440 bytes [entry] [rendered]
    > main [5] ./example.js 
    [0] ./~/a.js 11 bytes {3} [built]
        [no exports used]
        harmony import a [5] ./example.js 1:0-18
    [1] ./~/c async ^\.\/.*$ 160 bytes {3} [built]
        System.import context c [5] ./example.js 8:8-34
    [5] ./example.js 269 bytes {3} [built]