形参默认值

* 形参的默认值----当不传入参数的时候默认使用形参里的默认值
function Point(x = 1,y = 2) {
    this.x = x;
    this.y = y;
}

//定义一个点的坐标的构造函数
    function Point(x = 0, y = 0){
        this.x = x;
        this.y = y;
    }
    let point = new Point(23, 35);
    console.log(point);
    let point1 = new Point();
    console.log(point1);