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".

# 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

```javascript
/******/ (() => { // 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,
		[
			197
		]
	],
	"./1.js": [
		4,
		[
			197
		]
	],
	"./2": [
		5,
		[
			140
		]
	],
	"./2.js": [
		5,
		[
			140
		]
	]
};
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][0]).then(() => (__webpack_require__.t(id, 7 | 16)));
}
webpackAsyncContext.keys = () => (Object.keys(map));
webpackAsyncContext.id = 2;
module.exports = webpackAsyncContext;

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

<details><summary><code>/* webpack runtime code */</code></summary>

``` js
/************************************************************************/
/******/ 	// 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;
/******/ 		}
/******/ 		// Check if module exists (development only)
/******/ 		if (__webpack_modules__[moduleId] === undefined) {
/******/ 			var e = new Error("Cannot find module '" + moduleId + "'");
/******/ 			e.code = 'MODULE_NOT_FOUND';
/******/ 			throw e;
/******/ 		}
/******/ 		// 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' || typeof current == 'function') && !~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';
/******/ 				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 = {
/******/ 			792: 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);
/******/ 						}
/******/ 					}
/******/ 				}
/******/ 		};
/******/ 		
/******/ 		// 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[chunkId] = 0;
/******/ 			}
/******/ 		
/******/ 		}
/******/ 		
/******/ 		var chunkLoadingGlobal = self["webpackChunk"] = self["webpackChunk"] || [];
/******/ 		chunkLoadingGlobal.forEach(webpackJsonpCallback.bind(null, 0));
/******/ 		chunkLoadingGlobal.push = webpackJsonpCallback.bind(null, chunkLoadingGlobal.push.bind(chunkLoadingGlobal));
/******/ 	})();
/******/ 	
/************************************************************************/
```

</details>

``` js
var __webpack_exports__ = {};
// This entry needs to be wrapped in an IIFE because it needs 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() */ 414).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);
});

})();

/******/ })()
;
```

# Info

## Unoptimized

```
asset output.js 13.9 KiB [emitted] (name: main)
asset 140.output.js 284 bytes [emitted]
asset 197.output.js 284 bytes [emitted]
asset 414.output.js 276 bytes [emitted]
chunk (runtime: main) 140.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) 197.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) 414.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
chunk (runtime: main) output.js (main) 414 bytes (javascript) 6.89 KiB (runtime) [entry] [rendered]
  > ./example.js main
  runtime modules 6.89 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
webpack X.X.X compiled successfully
```

## Production mode

```
asset output.js 2.88 KiB [emitted] [minimized] (name: main)
asset 140.output.js 66 bytes [emitted] [minimized]
asset 197.output.js 66 bytes [emitted] [minimized]
asset 414.output.js 66 bytes [emitted] [minimized]
chunk (runtime: main) 140.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) 197.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) 414.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
chunk (runtime: main) output.js (main) 403 bytes (javascript) 6.63 KiB (runtime) [entry] [rendered]
  > ./example.js main
  runtime modules 6.63 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
webpack X.X.X compiled successfully
```