如何将参数传递给setTimeout函数 [英] How to pass parameters to setTimeout function

问题描述

我是javascript的新手.我编写了一个简单的计数器程序，该程序从10开始递减计数，直到达到1.

I am relatively novice to javascript. I have written a simple counter program that starts count down from 10 till it reaches 1.

  <script type="text/javascript">
    function countDown(secs) {
        var element = document.getElementById("status");
        element.innerHTML = "Please wait for "+secs+" seconds";
        if(secs < 1) {
            clearTimeout(timer);
            element.innerHTML = '<h2>Countdown Complete!</h2>';
            element.innerHTML += '<a href="#">Click here now</a>';
        }
        secs--;
 --->       **var timer = setTimeout('countDown('secs')',1000);**
    }
    </script>
    <div id="status"></div>
    <script type="text/javascript">countDown(10);</script>

然后我尝试将参数作为'+ secs +'传递给countDown函数.

Then I tried passing parameter as '+secs+' to the countDown function.

var timer = setTimeout('countDown('+secs+')',1000);

以上更改有效.

我的问题是，为什么我需要将参数传递为"+ secs +"而不是仅传递"secs"?有什么区别?

My question is why should I need to pass parameter as '+secs+' and NOT only 'secs' ? What difference does it make?

推荐答案

使用

var timer = setTimeout(function(){
        countDown(secs)
    },1000);

或

var timer = setTimeout('countDown('  + secs + ')',1000);

在您的情况下，问题是您使用带有不带 + 符号的变量的字符串连接(我的第二个示例)会导致语法错误

In your case the problem was your were using string concatenation with a variable without + sign (my second example) with will cause a syntactical error

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