javascript 原型继承

var Person= function(){
    this.name = ‘tom‘ ;
    this.age = 12 ;
} ;
Person.prototype.getName = function(){
    return this.name ;
} ;
Person.prototype.getAge =  function(){
    return this.age;
} ;

var Tom = function(){
    this.name = ‘child‘ ;
} ;
Tom .prototype = new Person() ;

var person= new Person() ;
var tom = new Tom ()