This example show how to use Code Splitting with the ES6 module syntax.
The standard import is sync.
import(module: string) -> Promise can be used to load modules on demand. This acts as a split point for webpack and creates a chunk.
Providing dynamic expressions to 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 import("c/" + name) creates two additional chunks (one for each file in node_modules/c/). This is called "async context".
import a from "a";
import("b").then(function(b) {
console.log("b loaded", b);
})
function loadC(name) {
return import("c/" + name);
}
Promise.all([loadC("1"), loadC("2")]).then(function(arr) {
console.log("c/1 and c/2 loaded", arr);
});/******/ (() => { // webpackBootstrap
/******/ var __webpack_modules__ = ([
/* 0 */,
/* 1 */
/*!***************************!*\
!*** ./node_modules/a.js ***!
\***************************/
/*! unknown exports (runtime-defined) */
/*! runtime requirements: */
/***/ (() => {
// module a
/***/ }),
/* 2 */
/*!********************************************************!*\
!*** ./node_modules/c/ lazy ^\.\/.*$ namespace object ***!
\********************************************************/
/*! default exports */
/*! exports [not provided] [no usage info] */
/*! runtime requirements: module, __webpack_require__.o, __webpack_require__, __webpack_require__.e, __webpack_require__.t, __webpack_require__.* */
/***/ ((module, __unused_webpack_exports, __webpack_require__) => {
var map = {
"./1": [
4,
346
],
"./1.js": [
4,
346
],
"./2": [
5,
98
],
"./2.js": [
5,
98
]
};
function webpackAsyncContext(req) {
if(!__webpack_require__.o(map, req)) {
return Promise.resolve().then(() => {
var e = new Error("Cannot find module '" + req + "'");
e.code = 'MODULE_NOT_FOUND';
throw e;
});
}
var ids = map[req], id = ids[0];
return __webpack_require__.e(ids[1]).then(() => {
return __webpack_require__.t(id, 7 | 16);
});
}
webpackAsyncContext.keys = () => (Object.keys(map));
webpackAsyncContext.id = 2;
module.exports = webpackAsyncContext;
/***/ })
/******/ ]);/* webpack runtime code */
/************************************************************************/
/******/ // The module cache
/******/ var __webpack_module_cache__ = {};
/******/
/******/ // The require function
/******/ function __webpack_require__(moduleId) {
/******/ // Check if module is in cache
/******/ var cachedModule = __webpack_module_cache__[moduleId];
/******/ if (cachedModule !== undefined) {
/******/ return cachedModule.exports;
/******/ }
/******/ // Create a new module (and put it into the cache)
/******/ var module = __webpack_module_cache__[moduleId] = {
/******/ // no module.id needed
/******/ // no module.loaded needed
/******/ exports: {}
/******/ };
/******/
/******/ // Execute the module function
/******/ __webpack_modules__[moduleId](module, module.exports, __webpack_require__);
/******/
/******/ // Return the exports of the module
/******/ return module.exports;
/******/ }
/******/
/******/ // expose the modules object (__webpack_modules__)
/******/ __webpack_require__.m = __webpack_modules__;
/******/
/************************************************************************/
/******/ /* webpack/runtime/compat get default export */
/******/ (() => {
/******/ // getDefaultExport function for compatibility with non-harmony modules
/******/ __webpack_require__.n = (module) => {
/******/ var getter = module && module.__esModule ?
/******/ () => (module['default']) :
/******/ () => (module);
/******/ __webpack_require__.d(getter, { a: getter });
/******/ return getter;
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/create fake namespace object */
/******/ (() => {
/******/ var getProto = Object.getPrototypeOf ? (obj) => (Object.getPrototypeOf(obj)) : (obj) => (obj.__proto__);
/******/ var leafPrototypes;
/******/ // 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 & 16: return value when it's Promise-like
/******/ // mode & 8|1: behave like require
/******/ __webpack_require__.t = function(value, mode) {
/******/ if(mode & 1) value = this(value);
/******/ if(mode & 8) return value;
/******/ if(typeof value === 'object' && value) {
/******/ if((mode & 4) && value.__esModule) return value;
/******/ if((mode & 16) && typeof value.then === 'function') return value;
/******/ }
/******/ var ns = Object.create(null);
/******/ __webpack_require__.r(ns);
/******/ var def = {};
/******/ leafPrototypes = leafPrototypes || [null, getProto({}), getProto([]), getProto(getProto)];
/******/ for(var current = mode & 2 && value; typeof current == 'object' && !~leafPrototypes.indexOf(current); current = getProto(current)) {
/******/ Object.getOwnPropertyNames(current).forEach((key) => (def[key] = () => (value[key])));
/******/ }
/******/ def['default'] = () => (value);
/******/ __webpack_require__.d(ns, def);
/******/ return ns;
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/define property getters */
/******/ (() => {
/******/ // define getter functions for harmony exports
/******/ __webpack_require__.d = (exports, definition) => {
/******/ for(var key in definition) {
/******/ if(__webpack_require__.o(definition, key) && !__webpack_require__.o(exports, key)) {
/******/ Object.defineProperty(exports, key, { enumerable: true, get: definition[key] });
/******/ }
/******/ }
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/ensure chunk */
/******/ (() => {
/******/ __webpack_require__.f = {};
/******/ // This file contains only the entry chunk.
/******/ // The chunk loading function for additional chunks
/******/ __webpack_require__.e = (chunkId) => {
/******/ return Promise.all(Object.keys(__webpack_require__.f).reduce((promises, key) => {
/******/ __webpack_require__.f[key](chunkId, promises);
/******/ return promises;
/******/ }, []));
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/get javascript chunk filename */
/******/ (() => {
/******/ // This function allow to reference async chunks
/******/ __webpack_require__.u = (chunkId) => {
/******/ // return url for filenames based on template
/******/ return "" + chunkId + ".output.js";
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/hasOwnProperty shorthand */
/******/ (() => {
/******/ __webpack_require__.o = (obj, prop) => (Object.prototype.hasOwnProperty.call(obj, prop))
/******/ })();
/******/
/******/ /* webpack/runtime/load script */
/******/ (() => {
/******/ var inProgress = {};
/******/ // data-webpack is not used as build has no uniqueName
/******/ // loadScript function to load a script via script tag
/******/ __webpack_require__.l = (url, done, key, chunkId) => {
/******/ if(inProgress[url]) { inProgress[url].push(done); return; }
/******/ var script, needAttach;
/******/ if(key !== undefined) {
/******/ var scripts = document.getElementsByTagName("script");
/******/ for(var i = 0; i < scripts.length; i++) {
/******/ var s = scripts[i];
/******/ if(s.getAttribute("src") == url) { script = s; break; }
/******/ }
/******/ }
/******/ if(!script) {
/******/ needAttach = true;
/******/ script = document.createElement('script');
/******/
/******/ script.charset = 'utf-8';
/******/ script.timeout = 120;
/******/ if (__webpack_require__.nc) {
/******/ script.setAttribute("nonce", __webpack_require__.nc);
/******/ }
/******/
/******/ script.src = url;
/******/ }
/******/ inProgress[url] = [done];
/******/ var onScriptComplete = (prev, event) => {
/******/ // avoid mem leaks in IE.
/******/ script.onerror = script.onload = null;
/******/ clearTimeout(timeout);
/******/ var doneFns = inProgress[url];
/******/ delete inProgress[url];
/******/ script.parentNode && script.parentNode.removeChild(script);
/******/ doneFns && doneFns.forEach((fn) => (fn(event)));
/******/ if(prev) return prev(event);
/******/ }
/******/ ;
/******/ var timeout = setTimeout(onScriptComplete.bind(null, undefined, { type: 'timeout', target: script }), 120000);
/******/ script.onerror = onScriptComplete.bind(null, script.onerror);
/******/ script.onload = onScriptComplete.bind(null, script.onload);
/******/ needAttach && document.head.appendChild(script);
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/make namespace object */
/******/ (() => {
/******/ // define __esModule on exports
/******/ __webpack_require__.r = (exports) => {
/******/ if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {
/******/ Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
/******/ }
/******/ Object.defineProperty(exports, '__esModule', { value: true });
/******/ };
/******/ })();
/******/
/******/ /* webpack/runtime/publicPath */
/******/ (() => {
/******/ __webpack_require__.p = "dist/";
/******/ })();
/******/
/******/ /* webpack/runtime/jsonp chunk loading */
/******/ (() => {
/******/ // no baseURI
/******/
/******/ // object to store loaded and loading chunks
/******/ // undefined = chunk not loaded, null = chunk preloaded/prefetched
/******/ // [resolve, reject, Promise] = chunk loading, 0 = chunk loaded
/******/ var installedChunks = {
/******/ 179: 0
/******/ };
/******/
/******/ __webpack_require__.f.j = (chunkId, promises) => {
/******/ // JSONP chunk loading for javascript
/******/ var installedChunkData = __webpack_require__.o(installedChunks, chunkId) ? installedChunks[chunkId] : undefined;
/******/ if(installedChunkData !== 0) { // 0 means "already installed".
/******/
/******/ // a Promise means "currently loading".
/******/ if(installedChunkData) {
/******/ promises.push(installedChunkData[2]);
/******/ } else {
/******/ if(true) { // all chunks have JS
/******/ // setup Promise in chunk cache
/******/ var promise = new Promise((resolve, reject) => (installedChunkData = installedChunks[chunkId] = [resolve, reject]));
/******/ promises.push(installedChunkData[2] = promise);
/******/
/******/ // start chunk loading
/******/ var url = __webpack_require__.p + __webpack_require__.u(chunkId);
/******/ // create error before stack unwound to get useful stacktrace later
/******/ var error = new Error();
/******/ var loadingEnded = (event) => {
/******/ if(__webpack_require__.o(installedChunks, chunkId)) {
/******/ installedChunkData = installedChunks[chunkId];
/******/ if(installedChunkData !== 0) installedChunks[chunkId] = undefined;
/******/ if(installedChunkData) {
/******/ var errorType = event && (event.type === 'load' ? 'missing' : event.type);
/******/ var realSrc = event && event.target && event.target.src;
/******/ error.message = 'Loading chunk ' + chunkId + ' failed.\n(' + errorType + ': ' + realSrc + ')';
/******/ error.name = 'ChunkLoadError';
/******/ error.type = errorType;
/******/ error.request = realSrc;
/******/ installedChunkData[1](error);
/******/ }
/******/ }
/******/ };
/******/ __webpack_require__.l(url, loadingEnded, "chunk-" + chunkId, chunkId);
/******/ } else installedChunks[chunkId] = 0;
/******/ }
/******/ }
/******/ };
/******/
/******/ // no prefetching
/******/
/******/ // no preloaded
/******/
/******/ // no HMR
/******/
/******/ // no HMR manifest
/******/
/******/ // no on chunks loaded
/******/
/******/ // install a JSONP callback for chunk loading
/******/ var webpackJsonpCallback = (parentChunkLoadingFunction, data) => {
/******/ var [chunkIds, moreModules, runtime] = data;
/******/ // add "moreModules" to the modules object,
/******/ // then flag all "chunkIds" as loaded and fire callback
/******/ var moduleId, chunkId, i = 0;
/******/ if(chunkIds.some((id) => (installedChunks[id] !== 0))) {
/******/ for(moduleId in moreModules) {
/******/ if(__webpack_require__.o(moreModules, moduleId)) {
/******/ __webpack_require__.m[moduleId] = moreModules[moduleId];
/******/ }
/******/ }
/******/ if(runtime) var result = runtime(__webpack_require__);
/******/ }
/******/ if(parentChunkLoadingFunction) parentChunkLoadingFunction(data);
/******/ for(;i < chunkIds.length; i++) {
/******/ chunkId = chunkIds[i];
/******/ if(__webpack_require__.o(installedChunks, chunkId) && installedChunks[chunkId]) {
/******/ installedChunks[chunkId][0]();
/******/ }
/******/ installedChunks[chunkIds[i]] = 0;
/******/ }
/******/
/******/ }
/******/
/******/ var chunkLoadingGlobal = self["webpackChunk"] = self["webpackChunk"] || [];
/******/ chunkLoadingGlobal.forEach(webpackJsonpCallback.bind(null, 0));
/******/ chunkLoadingGlobal.push = webpackJsonpCallback.bind(null, chunkLoadingGlobal.push.bind(chunkLoadingGlobal));
/******/ })();
/******/
/************************************************************************/var __webpack_exports__ = {};
// This entry need to be wrapped in an IIFE because it need to be in strict mode.
(() => {
"use strict";
/*!********************!*\
!*** ./example.js ***!
\********************/
/*! namespace exports */
/*! exports [not provided] [no usage info] */
/*! runtime requirements: __webpack_require__, __webpack_require__.n, __webpack_require__.r, __webpack_exports__, __webpack_require__.e, __webpack_require__.t, __webpack_require__.* */
__webpack_require__.r(__webpack_exports__);
/* harmony import */ var a__WEBPACK_IMPORTED_MODULE_0__ = __webpack_require__(/*! a */ 1);
/* harmony import */ var a__WEBPACK_IMPORTED_MODULE_0___default = /*#__PURE__*/__webpack_require__.n(a__WEBPACK_IMPORTED_MODULE_0__);
__webpack_require__.e(/*! import() */ 644).then(__webpack_require__.t.bind(__webpack_require__, /*! b */ 3, 23)).then(function(b) {
console.log("b loaded", b);
})
function loadC(name) {
return __webpack_require__(2)("./" + name);
}
Promise.all([loadC("1"), loadC("2")]).then(function(arr) {
console.log("c/1 and c/2 loaded", arr);
});
})();
/******/ })()
;asset output.js 13.6 KiB [emitted] (name: main)
asset 346.output.js 296 bytes [emitted]
asset 98.output.js 295 bytes [emitted]
asset 644.output.js 288 bytes [emitted]
chunk (runtime: main) 98.output.js 13 bytes [rendered]
> ./2 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2
> ./2.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2.js
./node_modules/c/2.js 13 bytes [optional] [built] [code generated]
[used exports unknown]
import() context element ./2 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2
import() context element ./2.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2.js
chunk (runtime: main) output.js (main) 414 bytes (javascript) 6.92 KiB (runtime) [entry] [rendered]
> ./example.js main
runtime modules 6.92 KiB 10 modules
dependent modules 171 bytes [dependent] 2 modules
./example.js 243 bytes [built] [code generated]
[no exports]
[used exports unknown]
entry ./example.js main
chunk (runtime: main) 346.output.js 13 bytes [rendered]
> ./1 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1
> ./1.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1.js
./node_modules/c/1.js 13 bytes [optional] [built] [code generated]
[used exports unknown]
import() context element ./1 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1
import() context element ./1.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1.js
chunk (runtime: main) 644.output.js 11 bytes [rendered]
> b ./example.js 3:0-11
./node_modules/b.js 11 bytes [built] [code generated]
[used exports unknown]
import() b ./example.js 3:0-11
webpack 5.51.1 compiled successfully
asset output.js 2.88 KiB [emitted] [minimized] (name: main)
asset 346.output.js 69 bytes [emitted] [minimized]
asset 644.output.js 69 bytes [emitted] [minimized]
asset 98.output.js 67 bytes [emitted] [minimized]
chunk (runtime: main) 98.output.js 13 bytes [rendered]
> ./2 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2
> ./2.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2.js
./node_modules/c/2.js 13 bytes [optional] [built] [code generated]
[used exports unknown]
import() context element ./2 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2
import() context element ./2.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./2.js
chunk (runtime: main) output.js (main) 403 bytes (javascript) 6.66 KiB (runtime) [entry] [rendered]
> ./example.js main
runtime modules 6.66 KiB 9 modules
dependent modules 160 bytes [dependent] 1 module
./example.js 243 bytes [built] [code generated]
[no exports]
[no exports used]
entry ./example.js main
chunk (runtime: main) 346.output.js 13 bytes [rendered]
> ./1 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1
> ./1.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1.js
./node_modules/c/1.js 13 bytes [optional] [built] [code generated]
[used exports unknown]
import() context element ./1 ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1
import() context element ./1.js ./node_modules/c/ lazy ^\.\/.*$ namespace object ./1.js
chunk (runtime: main) 644.output.js 11 bytes [rendered]
> b ./example.js 3:0-11
./node_modules/b.js 11 bytes [built] [code generated]
[used exports unknown]
import() b ./example.js 3:0-11
webpack 5.51.1 compiled successfully