webpack/examples/code-splitting-harmony/README.md

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 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".

# example.js

``` javascript
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);
});
```


# dist/output.js

<details><summary><code>/******/ (function(modules) { /* webpackBootstrap */ })</code></summary>

``` javascript
/******/ (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 = {
/******/ 		2: 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 = 2);
/******/ })
/************************************************************************/
```

</details>

``` javascript
/******/ ([
/* 0 */,
/* 1 */,
/* 2 */
/*!********************!*\
  !*** ./example.js ***!
  \********************/
/*! no exports provided */
/***/ (function(module, __webpack_exports__, __webpack_require__) {

"use strict";
__webpack_require__.r(__webpack_exports__);
/* harmony import */ var a__WEBPACK_IMPORTED_MODULE_0__ = __webpack_require__(/*! a */ 3);
/* harmony import */ var a__WEBPACK_IMPORTED_MODULE_0___default = /*#__PURE__*/__webpack_require__.n(a__WEBPACK_IMPORTED_MODULE_0__);


__webpack_require__.e(/*! import() */ 3).then(__webpack_require__.t.bind(null, /*! b */ 5, 7)).then(function(b) {
	console.log("b loaded", b);
})

function loadC(name) {
	return __webpack_require__(4)("./" + name);
}

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


/***/ }),
/* 3 */
/*!***************************!*\
  !*** ./node_modules/a.js ***!
  \***************************/
/*! no static exports found */
/***/ (function(module, exports) {

// module a

/***/ }),
/* 4 */
/*!*******************************************************!*\
  !*** ./node_modules/c lazy ^\.\/.*$ namespace object ***!
  \*******************************************************/
/*! no static exports found */
/***/ (function(module, exports, __webpack_require__) {

var map = {
	"./1": [
		0,
		0
	],
	"./1.js": [
		0,
		0
	],
	"./2": [
		1,
		1
	],
	"./2.js": [
		1,
		1
	]
};
function webpackAsyncContext(req) {
	var ids = map[req];
	if(!ids) {
		return Promise.resolve().then(function() {
			var e = new Error("Cannot find module '" + req + "'");
			e.code = 'MODULE_NOT_FOUND';
			throw e;
		});
	}
	return __webpack_require__.e(ids[1]).then(function() {
		var id = ids[0];
		return __webpack_require__.t(id, 7);
	});
}
webpackAsyncContext.keys = function webpackAsyncContextKeys() {
	return Object.keys(map);
};
webpackAsyncContext.id = 4;
module.exports = webpackAsyncContext;

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


# Info

## Unoptimized

```
Hash: 0a1b2c3d4e5f6a7b8c9d
Version: webpack 4.29.0
      Asset       Size  Chunks             Chunk Names
0.output.js  275 bytes       0  [emitted]  
1.output.js  284 bytes       1  [emitted]  
3.output.js  270 bytes       3  [emitted]  
  output.js    9.7 KiB       2  [emitted]  main
Entrypoint main = output.js
chunk    {0} 0.output.js 13 bytes <{2}> [rendered]
    > ./1 [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./1
    > ./1.js [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./1.js
    1 module
chunk    {1} 1.output.js 13 bytes <{2}> [rendered]
    > ./2 [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./2
    > ./2.js [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./2.js
    1 module
chunk    {2} output.js (main) 414 bytes >{0}< >{1}< >{3}< [entry] [rendered]
    > ./example.js main
 [2] ./example.js 243 bytes {2} [built]
     [no exports]
     single entry ./example.js  main
 [4] ./node_modules/c lazy ^\.\/.*$ namespace object 160 bytes {2} [built]
     import() context lazy c [2] ./example.js 8:8-27
     + 1 hidden module
chunk    {3} 3.output.js 11 bytes <{2}> [rendered]
    > b [2] ./example.js 3:0-11
    1 module
```

## Production mode

```
Hash: 0a1b2c3d4e5f6a7b8c9d
Version: webpack 4.29.0
      Asset      Size  Chunks             Chunk Names
0.output.js  76 bytes       0  [emitted]  
1.output.js  77 bytes       1  [emitted]  
3.output.js  78 bytes       3  [emitted]  
  output.js  2.52 KiB       2  [emitted]  main
Entrypoint main = output.js
chunk    {0} 0.output.js 13 bytes <{2}> [rendered]
    > ./1 [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./1
    > ./1.js [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./1.js
    1 module
chunk    {1} 1.output.js 13 bytes <{2}> [rendered]
    > ./2 [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./2
    > ./2.js [4] ./node_modules/c lazy ^\.\/.*$ namespace object ./2.js
    1 module
chunk    {2} output.js (main) 414 bytes >{0}< >{1}< >{3}< [entry] [rendered]
    > ./example.js main
 [2] ./example.js 243 bytes {2} [built]
     [no exports]
     single entry ./example.js  main
 [4] ./node_modules/c lazy ^\.\/.*$ namespace object 160 bytes {2} [built]
     import() context lazy c [2] ./example.js 8:8-27
     + 1 hidden module
chunk    {3} 3.output.js 11 bytes <{2}> [rendered]
    > b [2] ./example.js 3:0-11
    1 module
```