// 判断属性是否存在于实例对象中 for-in function Person(name, age) { this.name = name; this.age = 20; } var p = new Person(); console.log(‘name‘ in p) //true //判断一个属性是否存在原型中 function hasPrototypeProper(object, name) { return !object.hasOwnProperty(name) && name in object; }
原文：http://www.cnblogs.com/goweb/p/5650880.html