JavaScript之对原生JavaScript对象及其原型扩展初探

//扩展：对JavaScript原生对象的扩展
//原理：原型对象
Object.prototype.keys = function(){
var keys = [];
for(var item in this)
if(this.hasOwnProperty(item))//用于判断一个属性是否是对象实例定义的，还是从原型导入的
keys.push(item);
return keys;
}var obj = {"name":"johnny","age":21};
obj.keys();//["name"."age"]

Number.prototype.add = function(param){
return this + param;
}var n = 5;
n.add(3);//8