最简单的 webpack 打包后代码

webpack-module-loader.js

(function (modules) {
  // The module cache
  var installedModules = {};
  // The require function
  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] = {
      i: moduleId,
      l: false,
      exports: {},
    });

    // Execute the module function
    modules[moduleId].call(
      module.exports,
      module,
      module.exports,
      __webpack_require__
    );
    // Flag the module as loaded
    module.l = true;

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

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

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

  // define getter function for harmony exports
  __webpack_require__.d = function (exports, name, getter) {
    if (!__webpack_require__.o(exports, name)) {
      Object.defineProperty(exports, name, { enumerable: true, get: getter });
    }
  };

  // define __esModule on exports
  __webpack_require__.r = function (exports) {
    if (typeof Symbol !== 'undefined' && Symbol.toStringTag) {
      Object.defineProperty(exports, Symbol.toStringTag, { value: 'Module' });
    }
    Object.defineProperty(exports, '__esModule', { value: true });
  };

  // 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 & 8|1: behave like require
  __webpack_require__.t = function (value, mode) {
    if (mode & 1) value = __webpack_require__(value);
    if (mode & 8) return value;
    if (mode & 4 && typeof value === 'object' && value && value.__esModule)
      return value;
    var ns = Object.create(null);
    __webpack_require__.r(ns);
    Object.defineProperty(ns, 'default', { enumerable: true, value: value });
    if (mode & 2 && typeof value != 'string')
      for (var key in value)
        __webpack_require__.d(
          ns,
          key,
          function (key) {
            return value[key];
          }.bind(null, key)
        );
    return ns;
  };

  // getDefaultExport function for compatibility with non-harmony modules
  __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
  __webpack_require__.o = function (object, property) {
    return Object.prototype.hasOwnProperty.call(object, property);
  };

  // __webpack_public_path__
  __webpack_require__.p = '';

  // Load entry module and return exports
  return __webpack_require__((__webpack_require__.s = './demo1/index.js'));
})({
  './demo1/index.js': function (module, exports) {
    console.log('demo1/index.js');
  },
});

__webpack_require__ 是一个function，给这个function赋值一些变量。

然后执行__webpack_require__((__webpack_require__.s = './demo1/index.js'));，

由于没有.s这个变量，所以默认值还是./demo1/index.js

相当于：__webpack_require__('./demo1/index.js');