javascript - javascript 中的重写方法

Question

我的问题是我不明白为什么这个覆盖在这里不起作用

window.onload=function()
{
   function Person(first,last)
   {
      this.First=first;
      this.Last = last;
      this.Full=function()
      {
         return this.First+" "+this.Last;
      };
   }

   Person.prototype.GetFullName=function()
   {
      return this.First + " " + this.Last;
   } ;



   function Employee(first,last,position)
   {
      Person.call(this,first,last);
      this.Position=position;
   }
   /* Employee.prototype = new Person();
   var t = new Employee("Mohamed","Zaki","Web Developer");

   alert(t.GetFullName());
    */
   Employee.prototype.GetFullName=function()
   {
      var x = Person.prototype.GetFullName.call(this);
      return x + " , " + this.Position ; 
   }
   var e = new Employee("Mohamed","Zaki","Web Developer");
   alert(e.GetFullName());
   }

Answer 1

如果我理解你的问题，你注释掉的代码不起作用，因为它是在覆盖 GetFullName 之前执行的。

/* 
   **** this code is executed before GetFullName is overridden and will use
   **** original function 
   Employee.prototype = new Person();
   var t = new Employee("Mohamed","Zaki","Web Developer");

   alert(t.GetFullName());
    */

   Employee.prototype.GetFullName=function()
   {
      var x = Person.prototype.GetFullName.call(this);
      return x + " , " + this.Position ; 
   }

   /**** This code is executed after GetFullName is overridden uses the new version */
   var e = new Employee("Mohamed","Zaki","Web Developer");
   alert(e.GetFullName());
   }