John Resig在使用继承的_super之后，将原始的_super重新涂抹

Question

从：https://stackoverflow.com/a/15052240/1487102

向下滚动以查看我对

的线条

在应用之前声明继承的功能this._super是有道理的。

我没有得到的是：他执行功能并获得返回阀后，为什么他会用任何事先替换this._super？

？

评论说它只需要暂时声明，但是为什么不将其宣布为呢？我看不出如何改善垃圾收集或任何其他优化。

/* Simple JavaScript Inheritance for ES 5.1
 * based on http://ejohn.org/blog/simple-javascript-inheritance/
 *  (inspired by base2 and Prototype)
 * MIT Licensed.
 */
(function(global) {
  "use strict";
  var fnTest = /xyz/.test(function(){xyz;}) ? /b_superb/ : /.*/;
  // The base Class implementation (does nothing)
  function BaseClass(){}
  // Create a new Class that inherits from this class
  BaseClass.extend = function(props) {
    var _super = this.prototype;
    // Set up the prototype to inherit from the base class
    // (but without running the init constructor)
    var proto = Object.create(_super);
    // Copy the properties over onto the new prototype
    for (var name in props) {
      // Check if we're overwriting an existing function
      proto[name] = typeof props[name] === "function" && 
        typeof _super[name] == "function" && fnTest.test(props[name])
        ? (function(name, fn){
            return function() {
              var tmp = this._super;
              // Add a new ._super() method that is the same method
              // but on the super-class
              this._super = _super[name];
              // The method only need to be bound temporarily, so we
              // remove it when we're done executing
              var ret = fn.apply(this, arguments); 

             this._super = tmp;  // <------ why??

              return ret;
            };
          })(name, props[name])
        : props[name];
    }
    // The new constructor
    var newClass = typeof proto.init === "function"
      ? proto.hasOwnProperty("init")
        ? proto.init // All construction is actually done in the init method
        : function SubClass(){ _super.init.apply(this, arguments); }
      : function EmptyClass(){};
    // Populate our constructed prototype object
    newClass.prototype = proto;
    // Enforce the constructor to be what we expect
    proto.constructor = newClass;
    // And make this class extendable
    newClass.extend = BaseClass.extend;
    return newClass;
  };
  // export
  global.Class = BaseClass;
})(this);

Answer 1

关于 this所指的

的混乱

声明this._super = function时，整个类实例将具有一个键_super，该键指向特定功能（显然不需要）