js代码错误

Question

谁能告诉我为什么这个JS代码不起作用？

它应该每秒打印一次时间：

function stampajDatum(){
    var now = new Date();
    var sat = now.getHours();
    var mins = now.getMinutes();
    var sec = now.getSeconds();
    document.write(sat + ":" + mins + ":" + sec);
}
setInterval("stampajDatum()", 1000);

Answer 1

我在控制台中收到的第一条消息是关于该隐含评估的。 在setInterval("stampajDatum()", 1000);函数名称周围的引号setInterval("stampajDatum()", 1000); （将其setInterval(stampajDatum(), 1000); ）

我通常不使用setInterval() ，但是我知道setTimeout()可以工作。 这是一个例子：

function stampajDatum(){
    var now = new Date();
    var sat = now.getHours();
    var mins = now.getMinutes();
    var sec = now.getSeconds();
    document.write(sat + ":" + mins + ":" + sec);
    setTimeout(stampajDatum(), 1000);
}
stampajDatum();

Answer 2

function stampajDatum(){
    var now = new Date();
    var sat = now.getHours();
    var mins = now.getMinutes();
    var sec = now.getSeconds();
    document.write(sat + ":" + mins + ":" + sec);// the problem is here
    //This writes content to a place after script block
    //if the script is in head then nothing is visible.
    //use something like this:
    //document.getElementById('timer').innerHTML = sat + ":" + mins + ":" + sec;
}
setInterval("stampajDatum()", 1000);//This is OK but setInterval(stampajDatum, 1000); is better. 
//Note that there is no () after stampajDatum