Arrow function NA scene

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<head>
    <meta charset="UTF-8">
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    <title>arrow-function箭头函数不适用场景</title>
</head>

<body>
    <script>
        /*
        作为构造函数，一个方法需要绑定到对象
        */
        // const Person = (name, points) => {
        //     this.name = name; //this.name并没有绑定到xyz这个对象上
        //     this.points = points; //this.points并没有绑定到xyz这个对象上
        // }
        // const xyz = new Person('xyz', 7); //报错：Uncaught TypeError: Person is not a constructor...
        // /*
        //    箭头函数是不存在this值的绑定的;
        //    所以this.name并没有绑定到xyz这个对象上；
        // */
        // Person.prototype.updatePoints = () => {
        //     this.points++;
        //     console.log(this.points);
        // }

        const Person1 = function (name, points) {
            this.name = name;
            this.points = points;
        }
        const xyz1 = new Person1('xyz', 7);
        console.log(xyz1);
        Person1.prototype.updatePoints = () => {
            console.log(this); //window   注意这里也是使用的箭头函数，所以this指向的是父级作用域
            this.points++;
            console.log(this.points); //NaN
        }
        console.log(xyz1.updatePoints()); //undefined


        const Person2 = function (name, points) {
            this.name = name;
            this.points = points;
        }
        const xyz2 = new Person2('xyz', 7);
        Person2.prototype.updatePoints = function () {
            this.points++;
            console.log(this.points); //8
        }

        /*
        需要使用arguments对象
        */
    </script>
</body>

</html>
Arrow function NA scene

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