How to implement dynamic countdown effect in js

The steps for js to implement dynamic countdown effect: First, obtain the target time input by the user, and then obtain the current time, subtract the current time from the target time, and obtain the time difference; then, pass the obtained time difference to Convert it into days, hours, minutes, and seconds; finally, dynamically output the remaining time.

Let’s implement the dynamic countdown step by step:

1. Create a display style

html code:

<form>目的日期：<br><br>
     <input type="text" id="year"><span>年</span>
     <input type="text" id="month"><span>月</span>
     <input type="text" id="day"><span>日</span><br><br>
     <input type="text" id="hour"><span>时</span>
     <input type="text" id="minute"><span>分</span>
     <input type="text" id="second"><span>秒</span><br><br>
     <input type="button" value="确定" onclick="show()">
</form><br><br>
<div class="time1">还剩时间：<br><br>
     <span id="_d"></span>天 
     <span id="_h"></span>时
     <span id="_m"></span>分
     <span id="_s"></span>秒
</div>

css code:

input{width:50px;height: 20px;border:1px solid black;}
.time1 span{display:inline-block;width:40px;height: 20px;}

Rendering:

## 2. Implement dynamic countdown - js code

The first step: First, we need to get the target time . When we enter the target date on the page, click Confirm , get the target time.

function show(){
    //获取目的日期
    var myyear=document.getElementById("year").value;
    var mymonth=document.getElementById("month").value-1;
    var myday=document.getElementById("day").value;
    var myhour=document.getElementById("hour").value;
    var myminute=document.getElementById("minute").value;
    var mysecond=document.getElementById("second").value;
    var time=Number(new Date(myyear,mymonth,myday,myhour,myminute,mysecond));
}

Step 2: Get the current time, then subtract the current time from the target time, get the remaining time, which is the time difference.

//获取当前时间
 var nowTime=Date.now();

//获取时间差
var timediff=Math.round((time-nowTime)/1000);

Step 3: Convert the obtained time difference into days, hours, minutes and seconds

//获取还剩多少天
var day=parseInt(timediff/3600/24);

//获取还剩多少小时
var hour=parseInt(timediff/3600%24);

//获取还剩多少分钟
var minute=parseInt(timediff/60%60);

//获取还剩多少秒
var second=timediff%60;

Step 4: Output the remaining time

//输出还剩多少时间
document.getElementById("_d").innerHTML=day;
document.getElementById("_h").innerHTML=hour;
document.getElementById("_m").innerHTML=minute;
document.getElementById("_s").innerHTML=second;

Rendering:

#It is not a dynamic output at this time, and we still need to manually refresh it and enter the target date.

Step 5: Use timer setTimeout() to dynamically output time

setTimeout(show,1000);
if(timediff==0){return 0;}

When the time difference is 0, return 0 and stop output. You can also use the clearInterval() method to stop the timer and no longer continue to dynamically output the time:

 var set=setTimeout(show,1000);
if(timediff==0){clearInterval(set);}

When the time difference is 0, use the clearInterval() method to stop the setTimeout() timer and no longer output the time.

Dynamic renderings:

Description:

setInterval(): Define an interval Trigger a timer that calls a function or computes an expression at a specified period (in milliseconds). This method will continue to call the function until the clearInterval() method is called to stop the setInterval() timer or the window is closed.

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