在 JavaScript 中从头开始创建秒表

Question

通过为毫秒、秒和分钟创建变量，我想做一个小秒表项目。我的按钮 onClick 是 theTimer():

var milli = 0;
    var seconds = 0;
    var minutes = 0;
    var onOff = 0;

    var txtMilli = document.getElementById("txtMilli");
    var txtSeconds = document.getElementById("txtSeconds");
    var txtMinutes = document.getElementById("txtMinutes");

    function theTimer()
    {
        if (onOff == 0) {
            onOff = 1;
            timer = setInterval("startCounting()",1);
        }
        if (onOff == 1) {
            onOff == 0;
            clearInterval(timer);
        }
    }

    function startCounting()
    {
        if (milli >999) 
        { 
          milli = 0; if (seconds <60) {seconds +=1} 
        }
        else 
        {
          milli +=1;
        }
        if (seconds >59) 
        {
          seconds = 0; minutes += 1;
        }
        if (milli > 10) 
        {
          txtMilli.innerHTML = "0" + milli;
        }
        if (milli < 10) 
        {
          txtMilli.innerHTML = "" + milli;
        }
    }

控制台中没有显示任何内容，问题是当运行时 DIVs 永远不会从 0 改变。

Answer 1

我像这样修复了你的代码：

var milli = 0;
var seconds = 0;
var minutes = 0;
var onOff = 0;

var txtMilli = document.getElementById("txtMilli");
var txtSeconds = document.getElementById("txtSeconds");
var txtMinutes = document.getElementById("txtMinutes");

function startCounting(){        
    if (milli >999) { milli = 0; if (seconds <60) {seconds +=1} }
    else {milli +=1;}
    if (seconds >59) {seconds = 0; minutes += 1;}

    if (milli > 10) {txtMilli.innerHTML = "0" + milli;}
    if (milli < 10) {txtMilli.innerHTML = "" + milli;}
}

function theTimer(){
    if (onOff == 0) {
        onOff = 1;
        timer = setInterval(startCounting, 1);
    } else if (onOff == 1) {
        onOff = 0;
        clearInterval(timer);
    }
}

myButton.onclick = theTimer;

theTimer 中存在错误，您将 onOff 设置为 1，然后立即检查它是否为 1 并将其设置回0。我使用 else if 解决了这个问题。

我还把onOff == 0（比较）改成了onOff = 0（赋值）。

工作 JSFiddle：https://jsfiddle.net/k83tvfhc/

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