前端页面倒计时功能在很多场景中会用到，如很多秒杀活动等，本文主要介绍了用JS写了一个30分钟倒计时器的实现示例，感兴趣的可以了解一下
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html;charset=utf-8"/>
<title>Countdown Timer</title>
<style type="text/css">
input{
padding-bottom: 0px;
padding-top: 0px;
border-top-width: 0px;
border-left-width: 0px;
border-right-width: 0px;
font-size: 20px;
width:100%;
}
</style>
</head>
<body>
<span id="numbers" style="white-space:nowrap;"></span>
<table id="table1" >
<tr>
<td style="background-color:rgb(41, 74, 155);padding:3px;"></td>
<td></td>
</tr>
<tr>
<td style="width:100%;" colspan=2>
<input id="content"/>
</td>
</tr>
<tr>
<td style="width:100%;" colspan=2>
<canvas id="myCanvas" height="6">
Your browser does not support the canvas element.
</canvas>
</td>
</tr>
</table>
<audio id='music'>
<source src="https://www.atool.online/article/music/Windows XP 启动.wav" type="audio/mpeg">
Your browser does not support the audio tag.
</audio>
<audio id='music2'>
<source src="https://www.atool.online/article/music/Windows XP 关机.wav" type="audio/mpeg">
Your browser does not support the audio tag.
</audio>
<script type="text/javascript" >
var timer = {
initMinutes:30,
restSeconds:0,
minute:0,
second:0,
handle:0,
stopFlag:false,
startTime:0,
content:"asdasd",
coverFlag:false,
setFontSize:function(){
document.getElementById("numbers").style.fontSize = (window.innerWidth
|| document.documentElement.clientWidth
|| document.body.clientWidth) / 3 + "px"
},
refreshTable:function(){
//进度条
var table = document.getElementById("table1")
var span = document.getElementById('numbers')
//刷新进度条
//table2.style.width =
table.style.width = span.offsetWidth + "px"
var progress = 1
if(this.restSeconds > 0)
progress = this.restSeconds / (this.initMinutes * 60)
document.querySelector('#table1 td:nth-of-type(1)').style.width = progress * 100 + "%"
var td2 = document.querySelector('#table1 td:nth-of-type(2)')
if (progress < 1){
td2.style.width = (1 - progress) * 100 + "%"
}else{
td2.style.display = "none"
}
var canvas = document.getElementById('myCanvas')
canvas.width = span.offsetWidth
var ctx = canvas.getContext("2d")
var rectWeight = progress * span.offsetWidth
ctx.clearRect(0, 0, span.offsetWidth, 20)
ctx.fillStyle = "#FF0000"
//console.log("rectWeight: " + rectWeight)
//console.log(progress * span.offsetWidth)
ctx.fillRect(0, 0, rectWeight, 20)
},
init:function(){
this.startTime = Date.now()
var span = document.getElementById('numbers')
this.setFontSize()
this.restSeconds = this.initMinutes * 60
this.minute = this.initMinutes
var obj = this
this.handle = setInterval(function(){
if(obj.stopFlag)
return
if(obj.restSeconds > 0){
span.innerHTML = "" + (obj.minute < 10 ? "0" + obj.minute : obj.minute) + ":" +
(!obj.coverFlag ? (obj.second < 10 ? "0" + obj.second : obj.second) : " ".repeat(4))
if(obj.restSeconds > 0){
obj.restSeconds -= 1
}
obj.minute = Math.floor(obj.restSeconds / 60)
obj.second = obj.restSeconds - obj.minute * 60
//刷新进度条
obj.refreshTable()
}else{
span.innerHTML = "Time "
window.clearInterval(obj.handle)
document.getElementById("music2").play()
//跑完后记录
var content = document.getElementById("content").value
obj.markdownRecord(content)
//不停地闪烁
window.setInterval(function(){
span.innerHTML = (span.innerHTML == "Time ")?"is up.":"Time "
}, 5000)
}
}, 1000)
document.getElementById("music").play()
var numbers = document.getElementById("numbers")
numbers.addEventListener("click", function(){
obj.coverFlag = !obj.coverFlag
})
numbers.addEventListener("dblclick", function(){
obj.stopFlag = !obj.stopFlag
})
document.getElementById('content').addEventListener("blur", function(){
if(obj.restSeconds > 0)
return
var content = document.getElementById("content").value
if(this.content != content){
this.content = content
obj.markdownRecord(content)
}
})
document.getElementById('table1').addEventListener("dblclick", function(){
console.log("timerHistory:")
console.log(localStorage.getItem('timerHistory'))
console.log("\n")
obj.exportHistory()
})
},
markdownRecord:function(content){
var records = []
var timerHistory = localStorage.getItem("timerHistory")
if(timerHistory != null){
records = JSON.parse(timerHistory)
}
var lastRecord = records[0]
if(lastRecord && lastRecord.start == this.startTime){
lastRecord.note = content
}else{
var history = {
start:this.startTime,
duration:this.initMinutes,
note:content
}
records.unshift(history)//数组头插入元素
}
var recordsJson = JSON.stringify(records)
//将结果存入本地
localStorage.setItem("timerHistory", recordsJson)
console.log(records[0])
console.log("Marked it Down.")
},
exportHistory:function(){
var filename = 'record' + Date.now() +'.txt'
var text = localStorage.getItem('timerHistory')
this.exportFile(filename, text)
},
exportFile:function(filename, text){
var element = document.createElement('a');
element.setAttribute('href', 'data:text/plain;charset=utf-8,' + encodeURIComponent(text));
element.setAttribute('download', filename);
element.style.display = 'none';
document.body.appendChild(element);
element.click();
document.body.removeChild(element);
}
}
window.onresize = function(){
timer.setFontSize()
timer.refreshTable()
}
//pause
window.onclick = function(){
//timer.stopFlag = !timer.stopFlag
}
//main
window.onload = function(){
timer.init()
}
</script>
</body>
</html>
到此这篇关于用JS写了一个30分钟倒计时器的实现示例的文章就介绍到这了,更多相关JS 倒计时器内容请搜索阿兔在线工具以前的文章或继续浏览下面的相关文章希望大家以后多多支持阿兔在线工具！
