Question

我是javascript的新手，我想用localStorage创建一个倒数计时器，它从给定的时间开始，到00:00:00结束，但它不起作用，当我运行我的代码时，它显示的值为“1506”。

这是我的代码

program

Answer 1

您需要在Hour, Minute, Second, CurrentTime块旁边声明变量if else。在这种情况下，它们不在function CountDown()范围内。
您未在CurrentTime = Hour.toString() + ":" + Minute.toString() + ":" + Second.toString();

localStorage.setItem("counter", CurrentTime);

＆＃13;

var Hour = 3;
var Minute = 25;
var Second = 60;
var CurrentTime = Hour.toString() + ":" + Minute.toString() + ":" + Second.toString();


function CountDown() {
    document.getElementById('lblDuration').innerHTML = CurrentTime;
    Second--;
    if (Second == -1) {
        Second = 59;
        Minute--;
    }
    if (Minute == -1) {
        Minute = 59;
        Hour--;
    }
    CurrentTime = Hour.toString() + ":" + Minute.toString() + ":" + Second.toString();
}

setInterval(function () {
    CountDown();
}, 1000);

＆＃13;

<div id="lblDuration"></div>

＆＃13;

Answer 2

当localStorage可用时，您不需要设置小时，分钟和秒的值。因此，当执行倒计时功能时，它会发现Second未定义，而语句Second--将Second转换为NaN。要修复它，只需初始化小时，分钟和第二个变量。我已经重构了你的代码，希望它有所帮助：

function CountDown() { 
    var currentTime =  getCurrentTime();                           
    printCurrentTime(currentTime)
    currentTime.second--;
    if (currentTime.second == -1) {
        currentTime.second = 59;
        currentTime.minute--;
    }
    if (currentTime.minute == -1) {
        currentTime.minute = 59;
        currentTime.hour--;
    }
    setCurrentTime(currentTime);
}

  function setCurrentTime(newCurrentTime){
    if(localStorage) localStorage.setItem("counter", JSON.stringify(newCurrentTime));
    else setCurrentTime.storage = newCurrentTime;
  }
  function getCurrentTime(){
    var result = localStorage ? localStorage.getItem("counter") : setCurrentTime.storage;
    result = result || {hour:3, minute:25, second:60};
    if (typeof(result) === "string")result = JSON.parse(result);
    result.toString = function(){
        return result.hour +  ":" + result.minute + ":" + result.second;
    }
    return result;
  }
  function printCurrentTime(currentime){
        var domTag = document.getElementById('lblDuration');
        if(domTag) domTag.innerHTML = currentime.toString();
        else console.log(currentime);
  }
setInterval(function () { CountDown(); }, 1000);

倒数计时器未在javascript中显示

2 个答案: