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">
    <h1>{{ msg }}</h1>
    <h2>essential links</h2>
    <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>
    <h2>ecosystem</h2>
    <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;
}

h1, 
h2 { 
  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}h1,h2{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.$createelement;
    var _c = _vm._self._c || _h;
    return _c('div', {
      attrs: {
        "id": "app"
      }
    }, [_c('h1', [_vm._v(_vm._s(_vm.msg))]), _vm._v(" "), _c('h2', [_vm._v("essential links")]), _vm._v(" "), _vm._m(0, false, false), _vm._v(" "), _c('h2', [_vm._v("ecosystem")]), _vm._v(" "), _vm._m(1, false, false)])
  }
  var staticrenderfns = [function () {
    var _vm = this;
    var _h = _vm.$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);

  /***/
})