This example illustrates a very simple case of Code Splitting with require.ensure
.
a
andb
are required normally via CommonJSc
is depended through therequire.ensure
array.- This means: make it available, but don't execute it
- webpack will load it on demand
b
andd
are required via CommonJs in therequire.ensure
callback- webpack detects that these are in the on-demand-callback and
- will load them on demand
- webpacks optimizer can optimize
b
away- as it is already available through the parent chunks
You can see that webpack outputs two files/chunks:
output.js
is the entry chunk and contains- the module system
- chunk loading logic
- the entry point
example.js
- module
a
- module
b
1.output.js
is an additional chunk (on demand loaded) and contains- module
c
- module
d
- module
You can see that chunks are loaded via JSONP. The additional chunks are pretty small and minimize well.
var a = require("a");
var b = require("b");
require.ensure(["c"], function(require) {
require("b").xyz();
var d = require("d");
});
/******/ (function(modules) { /* webpackBootstrap */ })
/******/ (function(modules) { // webpackBootstrap
/******/ // install a JSONP callback for chunk loading
/******/ function webpackJsonpCallback(data) {
/******/ var chunkIds = data[0];
/******/ var moreModules = data[1];
/******/
/******/
/******/ // add "moreModules" to the modules object,
/******/ // then flag all "chunkIds" as loaded and fire callback
/******/ var moduleId, chunkId, i = 0, resolves = [];
/******/ 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(data);
/******/
/******/ while(resolves.length) {
/******/ resolves.shift()();
/******/ }
/******/
/******/ };
/******/
/******/
/******/ // The module cache
/******/ var installedModules = {};
/******/
/******/ // object to store loaded and loading chunks
/******/ // undefined = chunk not loaded, null = chunk preloaded/prefetched
/******/ // Promise = chunk loading, 0 = chunk loaded
/******/ var installedChunks = {
/******/ 0: 0
/******/ };
/******/
/******/
/******/
/******/ // script path function
/******/ function jsonpScriptSrc(chunkId) {
/******/ return __webpack_require__.p + "" + chunkId + ".output.js"
/******/ }
/******/
/******/ // 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) {
/******/ var promises = [];
/******/
/******/
/******/ // JSONP chunk loading for javascript
/******/
/******/ var installedChunkData = installedChunks[chunkId];
/******/ if(installedChunkData !== 0) { // 0 means "already installed".
/******/
/******/ // a Promise means "currently loading".
/******/ if(installedChunkData) {
/******/ promises.push(installedChunkData[2]);
/******/ } else {
/******/ // setup Promise in chunk cache
/******/ var promise = new Promise(function(resolve, reject) {
/******/ installedChunkData = installedChunks[chunkId] = [resolve, reject];
/******/ });
/******/ promises.push(installedChunkData[2] = promise);
/******/
/******/ // start chunk loading
/******/ var script = document.createElement('script');
/******/ var onScriptComplete;
/******/
/******/ script.charset = 'utf-8';
/******/ script.timeout = 120;
/******/ if (__webpack_require__.nc) {
/******/ script.setAttribute("nonce", __webpack_require__.nc);
/******/ }
/******/ script.src = jsonpScriptSrc(chunkId);
/******/
/******/ onScriptComplete = function (event) {
/******/ // avoid mem leaks in IE.
/******/ script.onerror = script.onload = null;
/******/ clearTimeout(timeout);
/******/ var chunk = installedChunks[chunkId];
/******/ if(chunk !== 0) {
/******/ if(chunk) {
/******/ var errorType = event && (event.type === 'load' ? 'missing' : event.type);
/******/ var realSrc = event && event.target && event.target.src;
/******/ var error = new Error('Loading chunk ' + chunkId + ' failed.\n(' + errorType + ': ' + realSrc + ')');
/******/ error.type = errorType;
/******/ error.request = realSrc;
/******/ chunk[1](error);
/******/ }
/******/ installedChunks[chunkId] = undefined;
/******/ }
/******/ };
/******/ var timeout = setTimeout(function(){
/******/ onScriptComplete({ type: 'timeout', target: script });
/******/ }, 120000);
/******/ script.onerror = script.onload = onScriptComplete;
/******/ document.head.appendChild(script);
/******/ }
/******/ }
/******/ return Promise.all(promises);
/******/ };
/******/
/******/ // expose the modules object (__webpack_modules__)
/******/ __webpack_require__.m = modules;
/******/
/******/ // expose the module cache
/******/ __webpack_require__.c = installedModules;
/******/
/******/ // define getter function for harmony exports
/******/ __webpack_require__.d = function(exports, name, getter) {
/******/ if(!__webpack_require__.o(exports, name)) {
/******/ Object.defineProperty(exports, name, { enumerable: true, get: getter });
/******/ }
/******/ };
/******/
/******/ // define __esModule on exports
/******/ __webpack_require__.r = function(exports) {
/******/ if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {
/******/ Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
/******/ }
/******/ Object.defineProperty(exports, '__esModule', { value: true });
/******/ };
/******/
/******/ // create a fake namespace object
/******/ // mode & 1: value is a module id, require it
/******/ // mode & 2: merge all properties of value into the ns
/******/ // mode & 4: return value when already ns object
/******/ // mode & 8|1: behave like require
/******/ __webpack_require__.t = function(value, mode) {
/******/ if(mode & 1) value = __webpack_require__(value);
/******/ if(mode & 8) return value;
/******/ if((mode & 4) && typeof value === 'object' && value && value.__esModule) return value;
/******/ var ns = Object.create(null);
/******/ __webpack_require__.r(ns);
/******/ Object.defineProperty(ns, 'default', { enumerable: true, value: value });
/******/ if(mode & 2 && typeof value != 'string') for(var key in value) __webpack_require__.d(ns, key, function(key) { return value[key]; }.bind(null, key));
/******/ return ns;
/******/ };
/******/
/******/ // 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 = "dist/";
/******/
/******/ // on error function for async loading
/******/ __webpack_require__.oe = function(err) { console.error(err); throw err; };
/******/
/******/ var jsonpArray = window["webpackJsonp"] = window["webpackJsonp"] || [];
/******/ var oldJsonpFunction = jsonpArray.push.bind(jsonpArray);
/******/ jsonpArray.push = webpackJsonpCallback;
/******/ jsonpArray = jsonpArray.slice();
/******/ for(var i = 0; i < jsonpArray.length; i++) webpackJsonpCallback(jsonpArray[i]);
/******/ var parentJsonpFunction = oldJsonpFunction;
/******/
/******/
/******/ // Load entry module and return exports
/******/ return __webpack_require__(__webpack_require__.s = 1);
/******/ })
/************************************************************************/
/******/ ([
/* 0 */
/*!***************************!*\
!*** ./node_modules/b.js ***!
\***************************/
/*! no static exports found */
/***/ (function(module, exports) {
// module b
/***/ }),
/* 1 */
/*!********************!*\
!*** ./example.js ***!
\********************/
/*! no static exports found */
/***/ (function(module, exports, __webpack_require__) {
var a = __webpack_require__(/*! a */ 2);
var b = __webpack_require__(/*! b */ 0);
__webpack_require__.e(/*! require.ensure */ 1).then((function(require) {
__webpack_require__(/*! b */ 0).xyz();
var d = __webpack_require__(/*! d */ 4);
}).bind(null, __webpack_require__)).catch(__webpack_require__.oe);
/***/ }),
/* 2 */
/*!***************************!*\
!*** ./node_modules/a.js ***!
\***************************/
/*! no static exports found */
/***/ (function(module, exports) {
// module a
/***/ })
/******/ ]);
(window["webpackJsonp"] = window["webpackJsonp"] || []).push([[1],[
/* 0 */,
/* 1 */,
/* 2 */,
/* 3 */
/*!***************************!*\
!*** ./node_modules/c.js ***!
\***************************/
/*! no static exports found */
/***/ (function(module, exports) {
// module c
/***/ }),
/* 4 */
/*!***************************!*\
!*** ./node_modules/d.js ***!
\***************************/
/*! no static exports found */
/***/ (function(module, exports) {
// module d
/***/ })
]]);
Minimized
(window.webpackJsonp=window.webpackJsonp||[]).push([[1],[,,,function(n,o){},function(n,o){}]]);
Hash: 0a1b2c3d4e5f6a7b8c9d
Version: webpack 4.29.0
Asset Size Chunks Chunk Names
1.output.js 490 bytes 1 [emitted]
output.js 8.69 KiB 0 [emitted] main
Entrypoint main = output.js
chunk {0} output.js (main) 161 bytes >{1}< [entry] [rendered]
> ./example.js main
[1] ./example.js 139 bytes {0} [built]
single entry ./example.js main
+ 2 hidden modules
chunk {1} 1.output.js 22 bytes <{0}> [rendered]
> [1] ./example.js 3:0-6:2
2 modules
Hash: 0a1b2c3d4e5f6a7b8c9d
Version: webpack 4.29.0
Asset Size Chunks Chunk Names
1.output.js 95 bytes 1 [emitted]
output.js 2.05 KiB 0 [emitted] main
Entrypoint main = output.js
chunk {0} output.js (main) 161 bytes >{1}< [entry] [rendered]
> ./example.js main
[1] ./example.js 139 bytes {0} [built]
single entry ./example.js main
+ 2 hidden modules
chunk {1} 1.output.js 22 bytes <{0}> [rendered]
> [1] ./example.js 3:0-6:2
2 modules