// 判断属性是否存在于实例对象中 for-infunction 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;}