* 形參的默認(rèn)值----當(dāng)不傳入?yún)?shù)的時(shí)候默認(rèn)使用形參里的默認(rèn)值
function Point(x = 1,y = 2) {
    this.x = x;
    this.y = y;
}

//定義一個(gè)點(diǎn)的坐標(biāo)的構(gòu)造函數(shù)
    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);