SOURCE

function getAge() {
    var y = new Date().getFullYear();
    console.log(y - this.birth);
}

var xiaoming = {
    name: '小明',
    birth: 1990,
    age: getAge
    f:function(){
  			console.log("fffff")
		}
};

xiaoming.age(); // 25
getAge.apply(xiaoming, []); // 25, this指向xiaoming, 参数为空
xiaoming.getAge()
//xiaoming.f.apply(null,[])