function Person(name){
  this.name = name;
  this.getName = function(){
    return this.name;
  }
}
function Artist(type){
  this.type = type;
  this.getType = function(){
    return this.type;
  }
}
Artist.prototype = new Person("arthinking");
var artist = new Artist("Guitar");
alert(artist.getType()); //本身就有type属性
alert(artist.getName()); //从Person原型链上继承到的属性和方法

var test1 = {
  name : "test1"
}
var test2 = {
  name : "test2"
}
function getName(){
  return this.name; //this根据传调用该函数的上下文来确定的，定义该函数时，this指针并不确定
}
alert(getName.call(test1));