JS对象的几个方法介绍

1.hasOwnProperty 判断是不是对象自身的属性，如果是继承的返回false否则true

function Fn(){
}
Fn.prototype.num = 10;
var obj = new Fn();
obj.id = 1;
console.log(obj.hasOwnProperty("id")); //true
console.log(obj.hasOwnProperty("num")); //false

2.constructor 返回对象的构造函数

var obj = new Function();
console.log(obj.constructor); //function Function() { [native code] }

3.instanceof 判断对象是否在某个构造函数上

var fn = new Function();
console.log(fn instanceof Function); //true
console.log(fn instanceof Object); //true
console.log(fn instanceof String); //false

4.toString 把对象转换成字符串

var arr = [1,2,3];
console.log(arr.toString()); //1,2,3