prototype 변천

setp1

    var Person = function () {};  // 
    var p = new Person();

setp1 변천:

     var Person = function () {};
     var p = new Person();  
      /*
      ==>   p.__proto__ = Person.prototype  ==> Person.call(p);
      */

setp1 변천 증명

    var Person = function () {};
    var p = new Person();
    alert(p.__proto__=== Person.prototype)     //true

setp2

     var Person = function () {};  // 
     Person.prototype.Say = function () {           // 
        alert("Person say")
     }
     var p = new Person();
     p.Say();

setp2 변천:

      var Person = function () {};  // 
      Person.prototype.Say = function () {           // 
         alert("Person say")
      }
      var p = new Person();  
      /*
       ==>   p.__proto__ = Person.prototype     ==>    Person.call(p);
      */
      p.Say();             
      /*
      ==>   p.Say() ( ！)    ==>   p.__proto__.Say() ( ) 
      */

setp2 변천 증명:

        var Person = function () {};
        var p = new Person();
        alert(p.Say=== Person.prototype.Say)     //true

step3

        var Person = function () {};       // 
        Person.prototype.Say = function () {     // 
             alert("Person say");
        }
        Person.prototype.Salary = 50000;     // 
        
        var Programmer = function () { };      // 
        Programmer.prototype = new Person();    
        Programmer.prototype.WriteCode = function () {   // 
            alert("programmer writes code");
        };
        Programmer.prototype.Salary = 500;     // 
        
        var p = new Programmer();
        p.Say();
        p.WriteCode();
        alert(p.Salary);
  

step3 변천:

        var Person = function () {};       // 
        Person.prototype.Say = function () {     // 
             alert("Person say");
        }
        Person.prototype.Salary = 50000;     // 
        
        var Programmer = function () { };      // 
        Programmer.prototype = new Person();    
        /*
         ==》 Programmer.prototype = p1 ( var p1 = new Person() )  
                //  ： p1.__proto__ ==  Person.prototype 
         ==>  Programmer.prototype.__proto__ == p1.__proto__ ==  Person.prototype
         ==》 Programmer.prototype.__proto__ = Person.prototype;
        */
        Programmer.prototype.WriteCode = function () {   // 
            alert("programmer writes code");
        };
        Programmer.prototype.Salary = 500;     // 
        
        var p = new Programmer();
        /*
            ==》p.__proto__ = Programmer.prototype ;       
           ==》 p.__proto__.__proto__ = Person.prototype     
        */
        p.Say();
        /*
          ==> p.Say()  ( Say)
          ==> p.__proto__.Say()( Say) 
            // p.__proto__ == Programmer.prototype ( Say)
          ==> p.__proto__.__proto__.Say() ( ！) 
            // p.__proto__.__proto__ = Person.prototype( Say） 
        */
        p.WriteCode();
        /*
           ==> p.WriteCode()  ( WriteCode)
           ==> p.__proto__.WriteCode  ( ！) // p.__proto__ == Programmer.prototype（ WriteCode） 
        */