webpack生成的这段代码起什么作用？什么时候会用到？

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

  // 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)
  }