詳解webpack分包及異步加載套路

 var path = require('path'),
 DashboardPlugin = require('webpack-dashboard/plugin'),
 HtmlWebpackPlugin = require('html-webpack-plugin'),
 webpack = require('webpack'),
 ExtractTextPlugin = require('extract-text-webpack-plugin');

var PATHS = {
 app: path.join(__dirname, 'src'),
 dist: path.join(__dirname, 'dist')
}

var PKG = require('./package.json');
var TARGET = process.env.npm_lifecycle_event; //獲取當(dāng)前正在運行的腳本名稱

var isProduction = function() {
 return process.env.NODE_ENV === 'production';
}



module.exports ={
 entry: {
 'index': path.join(__dirname, 'src/index.js'),
 'lib': ['./src/lib/js/index.js'],
 },
 //filename是主入口文件的名稱,即對應(yīng)的entry
 //chunkFilename對應(yīng)的是非主入口文件的名稱,chunk
 output: {
 path: PATHS.dist,
 publicPath: '/static/taxi-driver/', //publicPath 的話是打包的時候生成的文件鏈接,如果是在生產(chǎn)環(huán)境當(dāng)然是用服務(wù)器地址，如果是開發(fā)環(huán)境就是用本地靜態(tài)服務(wù)器的地址
 filename: 'js/register/[name].js',
 chunkFilename: 'js/register/[name].js',
 //TODO: build文件中加入hash值
 },
 //生成source-map文件
 devtool: isProduction ? null : 'source-map',
 devServer: {
 proxy: {
  '/api/*': {
  target: 'http://localhost:3000',
  secure: false
  }
 }
 },
 module: {
 loaders: [
  {
  test: /\.js$/,
  exclude: /node_modules|picker.min.js/,
  loader: 'babel'
  },
  {
  test: /\.less$/,
  loader: ExtractTextPlugin.extract('style', 'css!less')
  },
  {
  test: /\.html$/,
  loader: 'raw'
  },
  {
  test: /\.css$/,
  loader: ExtractTextPlugin.extract('style', 'css')
  },
  {
  test: /\.json$/,
  loader: 'json'
  }
 ]
 },
 resolve: {
 alias: {
  src: path.join(__dirname, 'src'),
  modules: path.join(__dirname, 'src/modules'),
  lessLib: path.join(__dirname, 'src/lib/less'), 
  jsLib: path.join(__dirname, 'src/lib/js'),
  components: path.join(__dirname, 'src/components')
 },
 extensions: ['', '.js', '.less', '.html', '.json'],
 },
 plugins: [
 new HtmlWebpackPlugin({
  title: '認(rèn)證資料',
  template: './dist/assets/info.html',
  inject: 'body',
  filename: 'pages/register/index.html' //輸出html文件的位置
 }),
 new DashboardPlugin(),
 new ExtractTextPlugin('css/register/style.css'), //將引入的樣式文件單獨抽成style.css文件并插入到head標(biāo)簽當(dāng)中,帶有路徑時,最后打包
 new webpack.optimize.CommonsChunkPlugin({
  name: 'common',
  filename: 'js/register/common.js',
  minChunks: 3
 })
 ]
}

 const Router = new Route();
 
 Route
 .addRoute({
  path: 'path2',
  viewBox: '.public-container',
  template: require('modules/path2/index.html'),
  pageInit() {
  //webpack提供的分包的API. require.ensure
  require.ensure([], () => {
   let controller = require('modules/path2/controller');
   Router.registerCtrl('path2', new controller('.public-container'));
  }, 'path2');
  }
 })
 .addRoute({
  path: 'path3',
  viewBox: '.public-container',
  template: require('modules/path3/index.html'),
  pageInit() {
  require.ensure([], () => {
   let controller = require('modules/path3/controller');
   Router.registerCtrl('path3', new controller('.public-container'));
  }, 'path3');
  }
 });

 //common.js
 (function(modules) {
 //modules用來保存所有的分包,它是一個數(shù)組,數(shù)組每個元素對應(yīng)的都是callback,每個分包都是通過數(shù)字來進(jìn)行標(biāo)識的
 
 //定義好的全局函數(shù)webpackJsonp
 //大家可以看看其他打包好的文件,例如index.js, path2.js和path3.js文件.都是webpackJsonp()這種的形式,大家用過JSONP應(yīng)該會很好理解。首先在前端定義好函數(shù)，然后后端下發(fā)組裝好的函數(shù)js文件,前端獲取到這個文件后就可以立即進(jìn)行執(zhí)行了
 var parentJsonpFunction = window["webpackJsonp"];
 window["webpackJsonp"] = function webpackJsonpCallback(chunkIds, moreModules) {
  var moduleId, chunkId, i = 0, callbacks = [];
 for(;i < chunkIds.length; i++) {
  chunkId = chunkIds[i];
  if(installedChunks[chunkId])
  callbacks.push.apply(callbacks, installedChunks[chunkId]);
  installedChunks[chunkId] = 0;
 }
  //這個全局函數(shù)會將各個分包緩存到modules
 for(moduleId in moreModules) {
  modules[moduleId] = moreModules[moduleId];
 }
 if(parentJsonpFunction) parentJsonpFunction(chunkIds, moreModules);
 while(callbacks.length)
  callbacks.shift().call(null, __webpack_require__);
  //用以啟動整個應(yīng)用
 if(moreModules[0]) {
  installedModules[0] = 0;
  return __webpack_require__(0);
 }
 };
 })([]);

 // The require function
  //通過數(shù)字標(biāo)識的moduleId
 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] = {
  exports: {},
  id: moduleId,
  loaded: false
 };

 // Execute the module function
 modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);

 // Flag the module as loaded
 module.loaded = true;

 // Return the exports of the module
 return module.exports;
 }

 // This file contains only the entry chunk.
 // The chunk loading function for additional chunks
  //異步加載函數(shù)
 __webpack_require__.e = function requireEnsure(chunkId, callback) {
 // "0" is the signal for "already loaded"
 if(installedChunks[chunkId] === 0)
  return callback.call(null, __webpack_require__);

 // an array means "currently loading".
 if(installedChunks[chunkId] !== undefined) {
  installedChunks[chunkId].push(callback);
 } else {
   //創(chuàng)建script表情,請求js文件
  // start chunk loading
  installedChunks[chunkId] = [callback];
  var head = document.getElementsByTagName('head')[0];
  var script = document.createElement('script');
  script.type = 'text/javascript';
  script.charset = 'utf-8';
  script.async = true;

  script.src = __webpack_require__.p + "js/register/" + ({"0":"index","1":"path2","2":"path3"}[chunkId]||chunkId) + ".js";
  head.appendChild(script);
 }
 };

 // expose the modules object (__webpack_modules__)
 __webpack_require__.m = modules;

 // expose the module cache
 __webpack_require__.c = installedModules;

 // __webpack_public_path__
  //配置文件中定義的publicPath,build完后加載文件的路徑
 __webpack_require__.p = "/static/taxi-driver/";
})

 webpackJsonp([0, 3], [
 /* 0 */
/***/ function(module, exports, __webpack_require__) {

 'use strict';

 __webpack_require__(1);

 __webpack_require__(8);

/***/ },
/* 1 */
/* 2 */
/* 3 */
//....
/* 8 */
 ])

 /* 0 */
 function(module, exports, __webpack_require__) {

 'use strict';

 __webpack_require__(1);

 __webpack_require__(8);

}

 /* 1 */
/***/ function(module, exports, __webpack_require__) {

 'use strict';

 Object.defineProperty(exports, "__esModule", {
 value: true
 });
 
 //加載路由庫
 var _index = __webpack_require__(2);
 //實例化一個路由
 var Router = new _index.Route();
 //定義好的路由規(guī)則
 Router.home('path2').addRoute({
 path: 'path2',
 viewBox: '.public-container',
 //模板文件,為模塊4
 template: __webpack_require__(4),
 pageInit: function pageInit() {
 //這個方法是在common.js中__webpack_require__的靜態(tài)方法,用來異步加載js。
 //異步加載js的文件（即chunk）用來數(shù)字來標(biāo)識，chunk的順序從0開始.
 //這里path2.js的chunk num為1,大家可以回過頭到common.js的__webpack_require__.e方法里面看看,里面已經(jīng)做好了chunk num和模塊文件的映射, chunk 1對應(yīng)的模塊文件為path2.js,chunk 2對用的模塊文件為path3.js
 //__webpack_require__.e()接收的第二個參數(shù)為異步加載模塊后的回調(diào). 當(dāng)path2.js被加載完后,在modules里面進(jìn)行了緩存.這時就可以通過模塊id去獲取這個模塊。然后進(jìn)行初始化等后續(xù)的操作
  __webpack_require__.e/* nsure */(1, function () {
  var controller = __webpack_require__(6);
  Router.registerCtrl('path2', new controller('.public-container'));
  });
 }
 }).addRoute({
 path: 'path3',
 viewBox: '.public-container',
 //模板文件,為模塊5
 template: __webpack_require__(5),
 pageInit: function pageInit() {
  __webpack_require__.e/* nsure */(2, function () {
  var controller = __webpack_require__(7);
  Router.registerCtrl('path3', new controller('.public-container'));
  });
 }
 });

 Router.bootstrap();

 exports.default = Router;

/***/ },