function Person (name){
 this.name = name;
}
Person.prototype.showName =function (){
 alert(this.name);
}
function Worker(name,job){
 Person.call(this,name);
 this.job = job;
}
extend(Worker.prototype, Person.prototype);
//如果用Worker.prototype=Person.prototype的话，会造成引用相同的问题
function extend(obj1,obj2){
 for(var i in obj2){
   obj1[i] = obj2[i]
 }
}
var coder = new Worker('magicfly','frontEnd');
coder.showName();

function Person (name){
 this.name = name;
}
Person.prototype.showName =function (){
 alert(this.name);
}
function Worker(name,job){
 Person.call(this,name);
 this.job = job;
}
//Worker.prototype = new Person();
// 这样继承会继承父级的不必要属性 
function F(){};
F.prototype = Person.prototype;
Worker.prototype = new F();
//通过建立一个临时构造函数来解决 ,也称为代理函数

var coder = new Worker('MAGICFLY','START');
coder.showName();

var a = {
  name : '小明'
};
var b = cloneObj(a);
b.name = '小强';
//alert( b.name );
alert( a.name );
function cloneObj(obj){
  var F = function(){};
  F.prototype = obj;
  return new F();
}