11.原型与原型链深入、对象继承

原型链的顶端 object.prototype
不是所有的对象都继承Object.prototype
例如

    var obj = Object.create(null)
    obj.num = 1;
    console.log(obj);

结果:

call/apply

    // call/apply 更改this的指向
    function Car(brand,color) {
        this.brand = brand;
        this.color = color;
        this.run = function () {
            console.log('running');
        }
    }
    var newCar = {
        displacement:"3.0"
    };
    // Car.call(newCar,'Benz','red');
    Car.apply(newCar,['Benz','red']);
    console.log(newCar);
    var car = new Car('Benz','red');
    console.log(car);

课后作业

    // 年龄为多少岁姓名为某买了一辆什么颜色什么品牌的车

        function Car(opt){
            this.color = opt.color;
            this.brand = opt.brand;
        }
        function Person(opt){
            Car.apply(this,arguments);
            this.names = opt.names;
            this.ages = opt.ages;
            this.select = function(){
                console.log(`年龄${this.ages}名字为:${this.names}买了一辆${this.color}色的${this.brand}`);
            }
        }
        var person = new Person({names:'小明',ages:15,color:'red',brand:'benz'});
        console.log(person);
        console.log(person.select());

参考答案

        function Car(brand,color,displacement) {
            this.brand = brand;
            this.color = color;
            this.displacement = displacement;
            this.info = function () {
                return '排量为' + this.displacement + '的' + this.color + this.brand
            }
        }
        function Person(opt) {
            Car.apply(this,[opt.name,opt.color,opt.displacement]); //此时this等于实例化的 p apply可以理解成借用函数 借用car里面的参数和方法
            this.name = opt.name;
            this.age = opt.age;
            this.say = function () {
                console.log('年龄'+this.age+'岁姓名为'+this.name+'卖了一辆'+this.info());
            }
        }
        var p = new Person({
            brand:'奔驰',
            color:'红色',
            displacement:'3.0',
            name:'张三',
            age:'25'
        })
        p.say();