//写出下面输出结果
var num1 = 1,num2 = 2;
    function cal() {
        var num1 = 10,num2 = 20;
        console.log(this.num1 + this.num2);
    }
    var calBind = cal.bind({num1:100,num2:200})
    new cal();
    cal();
    new calBind();
    calBind();