* 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 function Point(x=12, y=12) { this.x = x; this.y = y; } let point = new Point(25, 36); console.log(point); let p = new Point(); console.log(p); let point1 = new Point(12, 35); console.log(point1);