浅谈webpack编译vue项目生成的代码探索

import Vue from 'vue'; 
import App from './App.vue';

new Vue({ 
  el: '#app',
  template: '<App/>',
  components: {
    App
  }
})

<template> 
  <div id="app">
    <h2>{{ msg }}</h2>
    <h3>Essential Links</h3>
    <ul>
      <li>
        <a href="https://vuejs.org" rel="external nofollow" target="_blank">Core Docs</a>
      </li>
      <li>
        <a href="https://forum.vuejs.org" rel="external nofollow" target="_blank">Forum</a>
      </li>
      <li>
        <a href="https://chat.vuejs.org" rel="external nofollow" target="_blank">Community Chat</a>
      </li>
      <li>
        <a href="https://twitter.com/vuejs" rel="external nofollow" target="_blank">Twitter</a>
      </li>
    </ul>
    <h3>Ecosystem</h3>
    <ul>
      <li>
        <a href="http://router.vuejs.org/" rel="external nofollow" target="_blank">vue-router</a>
      </li>
      <li>
        <a href="http://vuex.vuejs.org/" rel="external nofollow" target="_blank">vuex</a>
      </li>
      <li>
        <a href="http://vue-loader.vuejs.org/" rel="external nofollow" target="_blank">vue-loader</a>
      </li>
      <li>
        <a href="https://github.com/vuejs/awesome-vue" rel="external nofollow" target="_blank">awesome-vue</a>
      </li>
    </ul>
  </div>
</template>

<script> 
export default { 
  name: 'app',
  data() {
    return {
      msg: 'Welcome to Your Vue.js App'
    }
  }
}
</script>

<style> 
#app {
  font-family: 'Avenir', Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-align: center;
  color: #2c3e50;
  margin-top: 60px;
}

h2, 
h3 { 
  font-weight: normal;
}

ul { 
  list-style-type: none;
  padding: 0;
}

li { 
  display: inline-block;
  margin: 0 10px;
}

a { 
  color: #42b983;
}
</style> 

npm run build

> learning-in-vue@1.0.0 build /Users/everlose/workspace/github/learningInVue
> cross-env NODE_ENV=production webpack --progress --hide-modules

Hash: 18d868a423b48dc263e9 
Version: webpack 3.9.1 
Time: 3693ms 
    Asset  Size Chunks          Chunk Names
  build.js 316 kB    0 [emitted] [big] main
build.js.map 399 kB    0 [emitted]     main 

/******/ (function(modules) { // webpackBootstrap
/******/   // The module cache
/******/   // 缓存模块，所有被加载过的模块都会成为installedModules对象的属性，靠函数__webpack_require__做到。
/******/   var installedModules = {};
/******/
/******/   // The require function 核心加载方法
/******/   function __webpack_require__(moduleId) {
/******/
/******/     // Check if module is in cache
/******/     // 检查模块是否已在缓存中，是则直接返回缓存中的模块不需要再次加载
/******/     if(installedModules[moduleId]) {
/******/       return installedModules[moduleId].exports;
/******/     }
/******/     // Create a new module (and put it into the cache)
/******/     // 创造一个新模块并放入缓存中，i是模块标识，l意为是否加载此模块完毕，exports是此模块执行后的输出对象
/******/     var module = installedModules[moduleId] = {
/******/       i: moduleId,
/******/       l: false,
/******/       exports: {}
/******/     };
/******/
/******/     // Execute the module function
/******/     // 传入参数并执行模块函数
/******/     modules[moduleId].call(module.exports, module, module.exports, __webpack_require__);
/******/
/******/     // Flag the module as loaded 标为true代表模块执行完成。
/******/     module.l = true;
/******/
/******/     // Return the exports of the module 返回此模块输出的对象
/******/     return module.exports;
/******/   }
/******/
/******/
/******/   // expose the modules object (__webpack_modules__)
/******/   // webpack 私有变量，保存传入的modules，即所有的模块组成的数组
/******/   __webpack_require__.m = modules;
/******/
/******/   // expose the module cache
/******/   // 保存缓存中的模块数组
/******/   __webpack_require__.c = installedModules;
/******/
/******/   // define getter function for harmony exports
/******/   // 为 es6 exports 定义 getter
/******/   __webpack_require__.d = function(exports, name, getter) {
/******/     // 如果 exports 输出的对象本身不包含 name 属性时，定义一个。
/******/     if(!__webpack_require__.o(exports, name)) {
/******/       Object.defineProperty(exports, name, {
/******/         configurable: false,
/******/         enumerable: true,
/******/         get: getter
/******/       });
/******/     }
/******/   };
/******/
/******/   // getDefaultExport function for compatibility with non-harmony modules
/******/   // 解决 ES module 和 Common js module 的冲突，ES 则返回 module['default']
/******/   __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
/******/   // 工具方法，判断是否object有property属性。
/******/   __webpack_require__.o = function(object, property) { return Object.prototype.hasOwnProperty.call(object, property); };
/******/
/******/   // __webpack_public_path__
/******/   // 大概和 webpack.config.js 的 output 有关吧，webpack 的公共路径
/******/   __webpack_require__.p = "/dist/";
/******/
/******/   // Load entry module and return exports 执行第一个依赖模块并且返回它输出。
/******/   return __webpack_require__(__webpack_require__.s = 0);
/******/ })

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

  var g;

  // This works in non-strict mode
  g = (function () {
    return this;
  })();

  try {
    // This works if eval is allowed (see CSP)
    g = g || Function("return this")() || (1, eval)("this");
  } catch (e) {
    // This works if the window reference is available
    if (typeof window === "object")
      g = window;
  }

  // g can still be undefined, but nothing to do about it...
  // We return undefined, instead of nothing here, so it's
  // easier to handle this case. if(!global) { ...}

  module.exports = g;


  /***/
}),

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

"use strict";
Object.defineProperty(__webpack_exports__, "__esModule", { value: true }); 
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_0_vue__ = __webpack_require__(2);
/* harmony import */ var __WEBPACK_IMPORTED_MODULE_1__App_vue__ = __webpack_require__(6);

// 从2号模块导出的一个叫a的变量，就是Vue对象本身
new __WEBPACK_IMPORTED_MODULE_0_vue__["a" /* default */]({ 
  el: '#app',
  template: '<App/>',
  components: {
    App: __WEBPACK_IMPORTED_MODULE_1__App_vue__["a" /* default */]
  }
});

/***/ })

/* 2 */
/***/ (function (module, __webpack_exports__, __webpack_require__) {

"use strict";
/*!
 * Vue.js v2.5.9
 * (c) 2014-2017 Evan You
 * Released under the MIT License.
 */

// 作用域指向__webpack_exports__，并把__webpack_require__(0)作为global，实际上就是window
// __webpack_require__(3).setImmediate)作为setsetImmediate参数传入函数
(function (global, setImmediate) {

  // 省略近1w行的代码，关于vue原本本身的解读以后再做......

  // 最终 export 出来一个叫 Vue$3的对象
  /* harmony default export */
  __webpack_exports__["a"] = (Vue$3);

  /* WEBPACK VAR INJECTION */
}.call(__webpack_exports__, __webpack_require__(0), __webpack_require__(3).setImmediate))

}),

/* 3 */
/***/
(function (module, exports, __webpack_require__) {

  // 省略代码...

  // setimmediate attaches itself to the global object
  __webpack_require__(4);
  exports.setImmediate = setImmediate;
  exports.clearImmediate = clearImmediate;

  /***/
}),

/* 4 */
/***/
(function (module, exports, __webpack_require__) {

  /* WEBPACK VAR INJECTION */
  (function (global, process) {
    // 省略代码...
  }.call(exports, __webpack_require__(0), __webpack_require__(5)))

  /***/
}),

/* 5 */
/***/
(function (module, exports) {

  // shim for using process in browser
  var process = module.exports = {};

  // 省略代码...

  process.cwd = function () {
    return '/'
  };
  process.chdir = function (dir) {
    throw new Error('process.chdir is not supported');
  };
  process.umask = function () {
    return 0;
  };
  /***/
}),

/* 6 */
/***/
(function (module, __webpack_exports__, __webpack_require__) {

  "use strict";

  // 返回具体 App.vue 中 的script 中的代码
  var __WEBPACK_IMPORTED_MODULE_0__babel_loader_node_modules_vue_loader_lib_selector_type_script_index_0_App_vue__ = __webpack_require__(13);

  // 把App.vue 的 template 解析为一堆 vue render 函数。
  var __WEBPACK_IMPORTED_MODULE_1__node_modules_vue_loader_lib_template_compiler_index_id_data_v_66ce2159_hasScoped_false_buble_transforms_node_modules_vue_loader_lib_selector_type_template_index_0_App_vue__ = __webpack_require__(14);

  // 注入vue文件里写入的css函数
  function injectStyle(ssrContext) {
    // 由此可知7号模块是编译并插入vue中的css到DOM上的
    __webpack_require__(7)
  }
  // 12号模块用于输出components渲染函数
  var normalizeComponent = __webpack_require__(12)
  /* script */

  /* template */

  /* template functional */
  var __vue_template_functional__ = false
  /* styles */
  var __vue_styles__ = injectStyle
  /* scopeId */
  var __vue_scopeId__ = null
  /* moduleIdentifier (server only) */
  var __vue_module_identifier__ = null

  // 编译模块，混杂template和script。
  var Component = normalizeComponent(
    __WEBPACK_IMPORTED_MODULE_0__babel_loader_node_modules_vue_loader_lib_selector_type_script_index_0_App_vue__["a" /* default */ ],
    __WEBPACK_IMPORTED_MODULE_1__node_modules_vue_loader_lib_template_compiler_index_id_data_v_66ce2159_hasScoped_false_buble_transforms_node_modules_vue_loader_lib_selector_type_template_index_0_App_vue__["a" /* default */ ],
    __vue_template_functional__,
    __vue_styles__,
    __vue_scopeId__,
    __vue_module_identifier__
  )

  /* harmony default export */
  __webpack_exports__["a"] = (Component.exports);


  /***/
}),

/* 7 */

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

  // style-loader: Adds some css to the DOM by adding a <style> tag

  // load the styles
  var content = __webpack_require__(8);
  if (typeof content === 'string') content = [
    [module.i, content, '']
  ];
  if (content.locals) module.exports = content.locals;
  // add the styles to the DOM
  var update = __webpack_require__(10)("15459d21", content, true);

  /***/
}),
/* 8 */
/***/
(function (module, exports, __webpack_require__) {

  // css-loader 用于做css的sourceMap
  exports = module.exports = __webpack_require__(9)(undefined);
  // imports


  // module
  // 这就是 App.vue 文件中 style 里的的 css
  exports.push([module.i, "#app{font-family:Avenir,Helvetica,Arial,sans-serif;-webkit-font-smoothing:antialiased;-moz-osx-font-smoothing:grayscale;text-align:center;color:#2c3e50;margin-top:60px}h2,h3{font-weight:400}ul{list-style-type:none;padding:0}li{display:inline-block;margin:0 10px}a{color:#42b983}", ""]);

  // exports


  /***/
}),
/* 9 */
/***/
(function (module, exports) {
  // css base code, injected by the css-loader
  module.exports = function (useSourceMap) {
    // 省略代码...
  }
}),
/* 10 */
/***/
(function (module, exports, __webpack_require__) {
  /*
    MIT License http://www.opensource.org/licenses/mit-license.php
    Author Tobias Koppers @sokra
    Modified by Evan You @yyx990803
  */

  // ...太长只贴了关键步骤，总之关键的函数就是这些
  var hasDocument = typeof document !== 'undefined'
  // ...
  var listToStyles = __webpack_require__(11)
  // ...
  var head = hasDocument && (document.head || document.getElementsByTagName('head')[0])


  // ...
  module.exports = function (parentId, list, _isProduction) {

    // ...
    var styles = listToStyles(parentId, list)
    addStylesToDom(styles)

    return function update (newList) {
      // ...
    }
  }

  function addStylesToDom (styles /* Array<StyleObject> */) {
    for (var i = 0; i < styles.length; i++) {
      // ...
      domStyle.parts.push(addStyle(item.parts[j]))
      // ....
    }
  }

  // 总之先调用了addStylesToDom，接着是addStyle，再是createStyleElement插入样式到head中。
  function createStyleElement () {
  var styleElement = document.createElement('style')
  styleElement.type = 'text/css'
  head.appendChild(styleElement)
  return styleElement
  }

  function addStyle (obj /* StyleObjectPart */) {
    // ...
    styleElement = createStyleElement()
    // ...
  }

  /***/
}),
/* 11 */
/***/
(function (module, exports) {

  /**
   * Translates the list format produced by css-loader into something
   * easier to manipulate.
   */
  module.exports = function listToStyles(parentId, list) {
    var styles = []
    var newStyles = {}
    for (var i = 0; i < list.length; i++) {
      var item = list[i]
      var id = item[0]
      var css = item[1]
      var media = item[2]
      var sourceMap = item[3]
      var part = {
        id: parentId + ':' + i,
        css: css,
        media: media,
        sourceMap: sourceMap
      }
      if (!newStyles[id]) {
        styles.push(newStyles[id] = {
          id: id,
          parts: [part]
        })
      } else {
        newStyles[id].parts.push(part)
      }
    }
    return styles
  }


  /***/
}),

Object 
  beforeCreate: [ƒ]
  data: ƒ data()
  inject: {}
  name: "app"
  render: ƒ ()
  staticRenderFns: (2) [ƒ, ƒ, cached: Array(2)]
  _Ctor: {0: ƒ}
  _compiled: true
  __proto__: Object

/* 12 */
/***/
(function (module, exports) {

  /* globals __VUE_SSR_CONTEXT__ */

  // IMPORTANT: Do NOT use ES2015 features in this file.
  // This module is a runtime utility for cleaner component module output and will
  // be included in the final webpack user bundle.

  module.exports = function normalizeComponent(
    rawScriptExports,
    compiledTemplate,
    functionalTemplate,
    injectStyles,
    scopeId,
    moduleIdentifier /* server only */
  ) {
    var esModule
    var scriptExports = rawScriptExports = rawScriptExports || {}

    // ES6 modules interop
    var type = typeof rawScriptExports.default
    if (type === 'object' || type === 'function') {
      esModule = rawScriptExports
      scriptExports = rawScriptExports.default
    }

    // Vue.extend constructor export interop
    var options = typeof scriptExports === 'function' ?
      scriptExports.options :
      scriptExports

    // render functions
    if (compiledTemplate) {
      options.render = compiledTemplate.render
      options.staticRenderFns = compiledTemplate.staticRenderFns
      options._compiled = true
    }

    // functional template
    if (functionalTemplate) {
      options.functional = true
    }

    // scopedId
    if (scopeId) {
      options._scopeId = scopeId
    }

    var hook
    if (moduleIdentifier) { // server build
      hook = function (context) {
        // 2.3 injection
        context =
          context || // cached call
          (this.$vnode && this.$vnode.ssrContext) || // stateful
          (this.parent && this.parent.$vnode && this.parent.$vnode.ssrContext) // functional
        // 2.2 with runInNewContext: true
        if (!context && typeof __VUE_SSR_CONTEXT__ !== 'undefined') {
          context = __VUE_SSR_CONTEXT__
        }
        // inject component styles
        if (injectStyles) {
          injectStyles.call(this, context)
        }
        // register component module identifier for async chunk inferrence
        if (context && context._registeredComponents) {
          context._registeredComponents.add(moduleIdentifier)
        }
      }
      // used by ssr in case component is cached and beforeCreate
      // never gets called
      options._ssrRegister = hook
    } else if (injectStyles) {
      hook = injectStyles
    }

    if (hook) {
      var functional = options.functional
      var existing = functional ?
        options.render :
        options.beforeCreate

      if (!functional) {
        // inject component registration as beforeCreate hook
        options.beforeCreate = existing ?
          [].concat(existing, hook) :
          [hook]
      } else {
        // for template-only hot-reload because in that case the render fn doesn't
        // go through the normalizer
        options._injectStyles = hook
        // register for functioal component in vue file
        options.render = function renderWithStyleInjection(h, context) {
          hook.call(context)
          return existing(h, context)
        }
      }
    }

    return {
      esModule: esModule,
      exports: scriptExports,
      options: options
    }
  }


  /***/
}),
/* 13 */
/***/
(function (module, __webpack_exports__, __webpack_require__) {

  "use strict";

  /* harmony default export */
  // 这就是 App.vue 中 script 的部分
  __webpack_exports__["a"] = ({
    name: 'app',
    data: function data() {
      return {
        msg: 'Welcome to Your Vue.js App'
      };
    }
  });

  /***/
}),
/* 14 */
/***/
(function (module, __webpack_exports__, __webpack_require__) {

  "use strict";
  // 把template 解析为一堆 render 函数，扔给vue处理最终编译成Vnode节点在渲染成DOM输出到视图
  var render = function () {
    var _vm = this;
    var _h = _vm.$createElement;
    var _c = _vm._self._c || _h;
    return _c('div', {
      attrs: {
        "id": "app"
      }
    }, [_c('h2', [_vm._v(_vm._s(_vm.msg))]), _vm._v(" "), _c('h3', [_vm._v("Essential Links")]), _vm._v(" "), _vm._m(0, false, false), _vm._v(" "), _c('h3', [_vm._v("Ecosystem")]), _vm._v(" "), _vm._m(1, false, false)])
  }
  var staticRenderFns = [function () {
    var _vm = this;
    var _h = _vm.$createElement;
    var _c = _vm._self._c || _h;
    return _c('ul', [_c('li', [_c('a', {
      attrs: {
        "href": "https://vuejs.org",
        "target": "_blank"
      }
    }, [_vm._v("Core Docs")])]), _vm._v(" "), _c('li', [_c('a', {
      attrs: {
        "href": "https://forum.vuejs.org",
        "target": "_blank"
      }
    }, [_vm._v("Forum")])]), _vm._v(" "), _c('li', [_c('a', {
      attrs: {
        "href": "https://chat.vuejs.org",
        "target": "_blank"
      }
    }, [_vm._v("Community Chat")])]), _vm._v(" "), _c('li', [_c('a', {
      attrs: {
        "href": "https://twitter.com/vuejs",
        "target": "_blank"
      }
    }, [_vm._v("Twitter")])])])
  }, function () {
    var _vm = this;
    var _h = _vm.$createElement;
    var _c = _vm._self._c || _h;
    return _c('ul', [_c('li', [_c('a', {
      attrs: {
        "href": "http://router.vuejs.org/",
        "target": "_blank"
      }
    }, [_vm._v("vue-router")])]), _vm._v(" "), _c('li', [_c('a', {
      attrs: {
        "href": "http://vuex.vuejs.org/",
        "target": "_blank"
      }
    }, [_vm._v("vuex")])]), _vm._v(" "), _c('li', [_c('a', {
      attrs: {
        "href": "http://vue-loader.vuejs.org/",
        "target": "_blank"
      }
    }, [_vm._v("vue-loader")])]), _vm._v(" "), _c('li', [_c('a', {
      attrs: {
        "href": "https://github.com/vuejs/awesome-vue",
        "target": "_blank"
      }
    }, [_vm._v("awesome-vue")])])])
  }]
  var esExports = {
    render: render,
    staticRenderFns: staticRenderFns
  }
  /* harmony default export */
  __webpack_exports__["a"] = (esExports);

  /***/
})