536 lines
17 KiB
Markdown
536 lines
17 KiB
Markdown
This example demonstrates Scope Hoisting in combination with Code Splitting.
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This is the dependency graph for the example: (solid lines express sync imports, dashed lines async imports)
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![](graph.png)
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All modules except `cjs` are EcmaScript modules. `cjs` is a CommonJs module.
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The interesting thing here is that putting all modules in single scope won't work, because of multiple reasons:
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- Modules `lazy`, `c`, `d` and `cjs` need to be in a separate chunk
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- Module `shared` is accessed by two chunks (different scopes)
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- Module `cjs` is a CommonJs module
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![](graph2.png)
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webpack therefore uses a approach called **"Partial Scope Hoisting"** or "Module concatenation", which chooses the largest possible subsets of ES modules which can be scope hoisted and combines them with the default webpack primitives.
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![](graph3.png)
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While module concatenation identifiers in modules are renamed to avoid conflicts and internal imports are simplified. External imports and exports from the root module use the existing ESM constructs.
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# example.js
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```javascript
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import { a, x, y } from "a";
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import * as b from "b";
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import("./lazy").then(function(lazy) {
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console.log(a, b.a(), x, y, lazy.c, lazy.d.a, lazy.x, lazy.y);
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});
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```
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# lazy.js
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```javascript
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export * from "c";
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import * as d from "d";
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export { d };
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```
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# a.js
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```javascript
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// module a
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export var a = "a";
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export * from "shared";
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```
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# b.js
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```javascript
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// module b
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export function a() {
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return "b";
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};
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```
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# c.js
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```javascript
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// module c
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import { c as e } from "cjs";
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export var c = String.fromCharCode(e.charCodeAt(0) - 2);
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export { x, y } from "shared";
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```
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# d.js
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```javascript
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// module d
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export var a = "d";
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```
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# cjs.js
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```javascript
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// module cjs (commonjs)
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exports.c = "e";
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```
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# shared.js
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```javascript
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// shared module
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export var x = "x";
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export * from "shared2";
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```
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# shared2.js
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```javascript
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// shared2 module
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export var y = "y";
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```
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# webpack.config.js
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```javascript
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module.exports = {
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// mode: "development" || "production",
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optimization: {
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usedExports: true,
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concatenateModules: true,
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occurrenceOrder: true // To keep filename consistent between different modes (for example building only)
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}
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};
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```
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# dist/output.js
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<details><summary><code>/******/ (function(modules) { /* webpackBootstrap */ })</code></summary>
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```javascript
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/******/ (function(modules) { // webpackBootstrap
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/******/ // install a JSONP callback for chunk loading
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/******/ function webpackJsonpCallback(data) {
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/******/ var chunkIds = data[0];
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/******/ var moreModules = data[1];
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/******/
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/******/
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/******/ // add "moreModules" to the modules object,
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/******/ // then flag all "chunkIds" as loaded and fire callback
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/******/ var moduleId, chunkId, i = 0, resolves = [];
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/******/ for(;i < chunkIds.length; i++) {
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/******/ chunkId = chunkIds[i];
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/******/ if(installedChunks[chunkId]) {
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/******/ resolves.push(installedChunks[chunkId][0]);
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/******/ }
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/******/ installedChunks[chunkId] = 0;
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/******/ }
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/******/ for(moduleId in moreModules) {
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/******/ if(Object.prototype.hasOwnProperty.call(moreModules, moduleId)) {
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/******/ modules[moduleId] = moreModules[moduleId];
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/******/ }
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/******/ }
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/******/ if(parentJsonpFunction) parentJsonpFunction(data);
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/******/
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/******/ while(resolves.length) {
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/******/ resolves.shift()();
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/******/ }
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/******/
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/******/ };
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/******/
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/******/
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/******/ // The module cache
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/******/ var installedModules = {};
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/******/
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/******/ // object to store loaded and loading chunks
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/******/ // undefined = chunk not loaded, null = chunk preloaded/prefetched
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/******/ // Promise = chunk loading, 0 = chunk loaded
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/******/ var installedChunks = {
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/******/ 0: 0
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/******/ };
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/******/
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/******/
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/******/
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/******/ // script path function
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/******/ function jsonpScriptSrc(chunkId) {
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/******/ return __webpack_require__.p + "" + chunkId + ".output.js"
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/******/ }
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/******/
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/******/ // The require function
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/******/ function __webpack_require__(moduleId) {
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/******/
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/******/ // Check if module is in cache
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/******/ if(installedModules[moduleId]) {
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/******/ return installedModules[moduleId].exports;
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/******/ }
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/******/ // Create a new module (and put it into the cache)
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/******/ var module = installedModules[moduleId] = {
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/******/ i: moduleId,
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/******/ l: false,
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/******/ exports: {}
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/******/ };
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/******/
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/******/ // Execute the module function
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/******/ modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
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/******/
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/******/ // Flag the module as loaded
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/******/ module.l = true;
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/******/
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/******/ // Return the exports of the module
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/******/ return module.exports;
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/******/ }
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/******/
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/******/ // This file contains only the entry chunk.
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/******/ // The chunk loading function for additional chunks
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/******/ __webpack_require__.e = function requireEnsure(chunkId) {
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/******/ var promises = [];
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/******/
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/******/
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/******/ // JSONP chunk loading for javascript
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/******/
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/******/ var installedChunkData = installedChunks[chunkId];
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/******/ if(installedChunkData !== 0) { // 0 means "already installed".
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/******/
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/******/ // a Promise means "currently loading".
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/******/ if(installedChunkData) {
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/******/ promises.push(installedChunkData[2]);
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/******/ } else {
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/******/ // setup Promise in chunk cache
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/******/ var promise = new Promise(function(resolve, reject) {
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/******/ installedChunkData = installedChunks[chunkId] = [resolve, reject];
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/******/ });
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/******/ promises.push(installedChunkData[2] = promise);
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/******/
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/******/ // start chunk loading
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/******/ var script = document.createElement('script');
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/******/ var onScriptComplete;
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/******/
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/******/ script.charset = 'utf-8';
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/******/ script.timeout = 120;
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/******/ if (__webpack_require__.nc) {
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/******/ script.setAttribute("nonce", __webpack_require__.nc);
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/******/ }
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/******/ script.src = jsonpScriptSrc(chunkId);
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/******/
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/******/ onScriptComplete = function (event) {
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/******/ // avoid mem leaks in IE.
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/******/ script.onerror = script.onload = null;
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/******/ clearTimeout(timeout);
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/******/ var chunk = installedChunks[chunkId];
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/******/ if(chunk !== 0) {
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/******/ if(chunk) {
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/******/ var errorType = event && (event.type === 'load' ? 'missing' : event.type);
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/******/ var realSrc = event && event.target && event.target.src;
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/******/ var error = new Error('Loading chunk ' + chunkId + ' failed.\n(' + errorType + ': ' + realSrc + ')');
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/******/ error.type = errorType;
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/******/ error.request = realSrc;
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/******/ chunk[1](error);
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/******/ }
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/******/ installedChunks[chunkId] = undefined;
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/******/ }
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/******/ };
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/******/ var timeout = setTimeout(function(){
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/******/ onScriptComplete({ type: 'timeout', target: script });
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/******/ }, 120000);
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/******/ script.onerror = script.onload = onScriptComplete;
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/******/ document.head.appendChild(script);
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/******/ }
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/******/ }
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/******/ return Promise.all(promises);
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/******/ };
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/******/
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/******/ // expose the modules object (__webpack_modules__)
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/******/ __webpack_require__.m = modules;
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/******/
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/******/ // expose the module cache
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/******/ __webpack_require__.c = installedModules;
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/******/
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/******/ // define getter function for harmony exports
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/******/ __webpack_require__.d = function(exports, name, getter) {
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/******/ if(!__webpack_require__.o(exports, name)) {
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/******/ Object.defineProperty(exports, name, { enumerable: true, get: getter });
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/******/ }
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/******/ };
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/******/
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/******/ // define __esModule on exports
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/******/ __webpack_require__.r = function(exports) {
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/******/ if(typeof Symbol !== 'undefined' && Symbol.toStringTag) {
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/******/ Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
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/******/ }
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/******/ Object.defineProperty(exports, '__esModule', { value: true });
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/******/ };
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/******/
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/******/ // create a fake namespace object
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/******/ // mode & 1: value is a module id, require it
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/******/ // mode & 2: merge all properties of value into the ns
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/******/ // mode & 4: return value when already ns object
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/******/ // mode & 8|1: behave like require
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/******/ __webpack_require__.t = function(value, mode) {
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/******/ if(mode & 1) value = __webpack_require__(value);
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/******/ if(mode & 8) return value;
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/******/ if((mode & 4) && typeof value === 'object' && value && value.__esModule) return value;
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/******/ var ns = Object.create(null);
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/******/ __webpack_require__.r(ns);
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/******/ Object.defineProperty(ns, 'default', { enumerable: true, value: value });
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/******/ if(mode & 2 && typeof value != 'string') for(var key in value) __webpack_require__.d(ns, key, function(key) { return value[key]; }.bind(null, key));
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/******/ return ns;
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/******/ };
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/******/
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/******/ // getDefaultExport function for compatibility with non-harmony modules
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/******/ __webpack_require__.n = function(module) {
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/******/ var getter = module && module.__esModule ?
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/******/ function getDefault() { return module['default']; } :
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/******/ function getModuleExports() { return module; };
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/******/ __webpack_require__.d(getter, 'a', getter);
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/******/ return getter;
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/******/ };
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/******/
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/******/ // Object.prototype.hasOwnProperty.call
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/******/ __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
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/******/
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/******/ // __webpack_public_path__
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/******/ __webpack_require__.p = "dist/";
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/******/
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/******/ // on error function for async loading
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/******/ __webpack_require__.oe = function(err) { console.error(err); throw err; };
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/******/
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/******/ var jsonpArray = window["webpackJsonp"] = window["webpackJsonp"] || [];
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/******/ var oldJsonpFunction = jsonpArray.push.bind(jsonpArray);
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/******/ jsonpArray.push = webpackJsonpCallback;
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/******/ jsonpArray = jsonpArray.slice();
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/******/ for(var i = 0; i < jsonpArray.length; i++) webpackJsonpCallback(jsonpArray[i]);
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/******/ var parentJsonpFunction = oldJsonpFunction;
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/******/
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/******/
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/******/ // Load entry module and return exports
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/******/ return __webpack_require__(__webpack_require__.s = 1);
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/******/ })
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/************************************************************************/
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```
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</details>
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```javascript
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/******/ ([
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/* 0 */
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/*!********************************************!*\
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!*** ./node_modules/shared.js + 1 modules ***!
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\********************************************/
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/*! exports provided: x, y */
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/*! exports used: x, y */
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/***/ (function(module, __webpack_exports__, __webpack_require__) {
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"use strict";
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// CONCATENATED MODULE: ./node_modules/shared2.js
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// shared2 module
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var y = "y";
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// CONCATENATED MODULE: ./node_modules/shared.js
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/* harmony export (binding) */ __webpack_require__.d(__webpack_exports__, "a", function() { return x; });
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/* concated harmony reexport y */__webpack_require__.d(__webpack_exports__, "b", function() { return y; });
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// shared module
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var x = "x";
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/***/ }),
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/* 1 */
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/*!********************************!*\
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!*** ./example.js + 2 modules ***!
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\********************************/
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/*! no exports provided */
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/*! all exports used */
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/*! ModuleConcatenation bailout: Cannot concat with ./node_modules/shared.js because of ./node_modules/c.js */
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/***/ (function(module, __webpack_exports__, __webpack_require__) {
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"use strict";
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__webpack_require__.r(__webpack_exports__);
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// EXTERNAL MODULE: ./node_modules/shared.js + 1 modules
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var shared = __webpack_require__(0);
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// CONCATENATED MODULE: ./node_modules/a.js
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// module a
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var a = "a";
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// CONCATENATED MODULE: ./node_modules/b.js
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// module b
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function b_a() {
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return "b";
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};
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// CONCATENATED MODULE: ./example.js
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__webpack_require__.e(/*! import() */ 1).then(__webpack_require__.bind(null, /*! ./lazy */ 3)).then(function(lazy) {
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console.log(a, b_a(), shared["a" /* x */], shared["b" /* y */], lazy.c, lazy.d.a, lazy.x, lazy.y);
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});
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/***/ })
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/******/ ]);
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```
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# dist/1.output.js
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```javascript
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(window["webpackJsonp"] = window["webpackJsonp"] || []).push([[1],[
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/* 0 */,
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/* 1 */,
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/* 2 */
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/*!*****************************!*\
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!*** ./node_modules/cjs.js ***!
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\*****************************/
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/*! no static exports found */
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/*! exports used: c */
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/*! ModuleConcatenation bailout: Module is not an ECMAScript module */
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/***/ (function(module, exports) {
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// module cjs (commonjs)
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exports.c = "e";
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/***/ }),
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/* 3 */
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/*!*****************************!*\
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!*** ./lazy.js + 2 modules ***!
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\*****************************/
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/*! exports provided: d, c, x, y */
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/*! all exports used */
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/*! ModuleConcatenation bailout: Cannot concat with ./node_modules/cjs.js (<- Module is not an ECMAScript module) */
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/*! ModuleConcatenation bailout: Cannot concat with ./node_modules/shared.js */
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/***/ (function(module, __webpack_exports__, __webpack_require__) {
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"use strict";
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__webpack_require__.r(__webpack_exports__);
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var d_namespaceObject = {};
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__webpack_require__.r(d_namespaceObject);
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__webpack_require__.d(d_namespaceObject, "a", function() { return a; });
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// EXTERNAL MODULE: ./node_modules/cjs.js
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var cjs = __webpack_require__(2);
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// EXTERNAL MODULE: ./node_modules/shared.js + 1 modules
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var shared = __webpack_require__(0);
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// CONCATENATED MODULE: ./node_modules/c.js
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// module c
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var c = String.fromCharCode(cjs["c"].charCodeAt(0) - 2);
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// CONCATENATED MODULE: ./node_modules/d.js
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// module d
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var a = "d";
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// CONCATENATED MODULE: ./lazy.js
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/* concated harmony reexport c */__webpack_require__.d(__webpack_exports__, "c", function() { return c; });
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/* concated harmony reexport x */__webpack_require__.d(__webpack_exports__, "x", function() { return shared["a" /* x */]; });
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/* concated harmony reexport y */__webpack_require__.d(__webpack_exports__, "y", function() { return shared["b" /* y */]; });
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/* concated harmony reexport d */__webpack_require__.d(__webpack_exports__, "d", function() { return d_namespaceObject; });
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/***/ })
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]]);
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```
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Minimized
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```javascript
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(window.webpackJsonp=window.webpackJsonp||[]).push([[1],[,,function(n,r){r.c="e"},function(n,r,t){"use strict";t.r(r);var c={};t.r(c),t.d(c,"a",function(){return e});var o=t(2),u=t(0),d=String.fromCharCode(o.c.charCodeAt(0)-2),e="d";t.d(r,"c",function(){return d}),t.d(r,"x",function(){return u.a}),t.d(r,"y",function(){return u.b}),t.d(r,"d",function(){return c})}]]);
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```
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# Info
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## Unoptimized
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```
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Hash: 0a1b2c3d4e5f6a7b8c9d
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Version: webpack 4.29.6
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Asset Size Chunks Chunk Names
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1.output.js 1.9 KiB 1 [emitted]
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output.js 9.41 KiB 0 [emitted] main
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Entrypoint main = output.js
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chunk {0} output.js (main) 372 bytes >{1}< [entry] [rendered]
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> ./example.js main
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[0] ./node_modules/shared.js + 1 modules 100 bytes {0} [built]
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[exports: x, y]
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[all exports used]
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harmony side effect evaluation shared [1] ./example.js + 2 modules 3:0-23
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harmony export imported specifier shared [1] ./example.js + 2 modules 3:0-23
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harmony side effect evaluation shared [3] ./lazy.js + 2 modules 6:0-30
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harmony export imported specifier shared [3] ./lazy.js + 2 modules 6:0-30
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harmony export imported specifier shared [3] ./lazy.js + 2 modules 6:0-30
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| 2 modules
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[1] ./example.js + 2 modules 272 bytes {0} [built]
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[no exports]
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single entry ./example.js main
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| ./example.js 161 bytes [built]
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| [no exports]
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| single entry ./example.js main
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| + 2 hidden modules
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chunk {1} 1.output.js 273 bytes <{0}> [rendered]
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> ./lazy [] 4:0-16
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[3] ./lazy.js + 2 modules 231 bytes {1} [built]
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[exports: d, c, x, y]
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import() ./lazy ./example.js 4:0-16
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| ./lazy.js 57 bytes [built]
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| [exports: d, c, x, y]
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| import() ./lazy ./example.js 4:0-16
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| + 2 hidden modules
|
|
+ 1 hidden module
|
|
```
|
|
|
|
## Production mode
|
|
|
|
```
|
|
Hash: 0a1b2c3d4e5f6a7b8c9d
|
|
Version: webpack 4.29.6
|
|
Asset Size Chunks Chunk Names
|
|
1.output.js 369 bytes 1 [emitted]
|
|
output.js 2.17 KiB 0 [emitted] main
|
|
Entrypoint main = output.js
|
|
chunk {0} output.js (main) 372 bytes >{1}< [entry] [rendered]
|
|
> ./example.js main
|
|
[0] ./node_modules/shared.js + 1 modules 100 bytes {0} [built]
|
|
[exports: x, y]
|
|
[all exports used]
|
|
harmony side effect evaluation shared [1] ./example.js + 2 modules 3:0-23
|
|
harmony export imported specifier shared [1] ./example.js + 2 modules 3:0-23
|
|
harmony side effect evaluation shared [3] ./lazy.js + 2 modules 6:0-30
|
|
harmony export imported specifier shared [3] ./lazy.js + 2 modules 6:0-30
|
|
harmony export imported specifier shared [3] ./lazy.js + 2 modules 6:0-30
|
|
| 2 modules
|
|
[1] ./example.js + 2 modules 272 bytes {0} [built]
|
|
[no exports]
|
|
single entry ./example.js main
|
|
| ./example.js 161 bytes [built]
|
|
| [no exports]
|
|
| single entry ./example.js main
|
|
| + 2 hidden modules
|
|
chunk {1} 1.output.js 273 bytes <{0}> [rendered]
|
|
> ./lazy [] 4:0-16
|
|
[3] ./lazy.js + 2 modules 231 bytes {1} [built]
|
|
[exports: d, c, x, y]
|
|
import() ./lazy ./example.js 4:0-16
|
|
| ./lazy.js 57 bytes [built]
|
|
| [exports: d, c, x, y]
|
|
| import() ./lazy ./example.js 4:0-16
|
|
| + 2 hidden modules
|
|
+ 1 hidden module
|
|
```
|