19 tostring()

• 当我们直接在页面中打印一个对象，实际上是输出对象的toString()方法的返回值

function Person(name,age,gender){
	this.name = name;
	this.age = age;
	this.gender = gender;
}

//修改原型的toString
Person.prototype.toString = function(){
	return "person[name]="+this.name+",age = "+this.age+",gender = "+gender;
}

var per = new Person("孙悟空",18,"男");
//修改对象的toString
per.toString = function(){
	return "我是个快乐的小Person";
}

console.log(per);         //输出[object object]    console.log(per);相当于输出了per.toString()

等同于

var result = per.toString();
console.log(result);     //输出[object object]

console.log(per.__proto__.__proto__.hasOwnProperty("toString"));     //输出true toString存在于原型的原型中
console.log(per);        //输出  我是个快乐的小Person