function test(str){
    this.name = str;
    this.number;
    this.setNum();//這行出事

    this.setNum = function(){
        this.number = 1;
    }
}
//直接執行
var t = new test("a");
// 然後就卡在this.setNum了

//假設我把this.setNum() 這段拿掉
var t = new test("a");
t.setNum(); 
// 正常執行:t.number = 1