圆环倒计时我们经常见到，实现的方法也有很多种。但是本文将介绍一种全新的实现方式，使用SVG来实现倒计时功能。
本文主要用到了SVG的stroke-dasharray和stroke-dashoffset特性。下图是倒计时运行效果：
SVG倒计时案例
下面说说相关的实现代码。css实现代码如下：
svg { transform: rotate(-0.05deg);}circle { transition: stroke-dasharray .2s;}.time-count-x { line-height: 1.5; position: relative;}.time-second { position: absolute; top: 50%; left: 0; right: 0; margin-top: -.75em; text-align: center; font-size: 100px;}相关html代码如下：
< div id="timeCountX" class="time-count-x" > < svg width="440" height="440" viewBox="0 0 440 440" class="center" > < defs > < linearGradient x1="1" y1="0" x2="0" y2="0" id="gradient1" > < stop offset="0%" stop-color="#e52c5c" >< /stop > < stop offset="100%" stop-color="#ab5aea" >< /stop > < /linearGradient > < linearGradient x1="1" y1="0" x2="0" y2="0" id="gradient2" > < stop offset="0%" stop-color="#4352f3" >< /stop > < stop offset="100%" stop-color="#ab5aea" >< /stop > < /linearGradient > < /defs > < g transform="matrix(0,-1,1,0,0,440)" > < circle cx="220" cy="220" r="170" stroke-width="50" stroke="#f0f1f5" fill="none" stroke-dasharray="1069 1069" >< /circle > < circle cx="220" cy="220" r="170" stroke-width="50" stroke="url('#gradient1')" fill="none" stroke-dasharray="1069 1069" >< /circle > < circle cx="220" cy="220" r="170" stroke-width="50" stroke="url('#gradient2')" fill="none" stroke-dasharray="534.5 1069" >< /circle > < /g > < /svg > < span id="timeSecond" class="time-second" >< /span >< /div >最后是相关JavaScript代码：
var eleCircles=document.querySelectorAll("#timeCountX circle");var eleTimeSec=document.getElementById("timeSecond");var perimeter=Math.PI*2*170;var circleInit=function(){ if(eleCircles[1]){ eleCircles[1].setAttribute("stroke-dasharray","1069 1069") } if(eleCircles[2]){ eleCircles[2].setAttribute("stroke-dasharray",perimeter/2+" 1069") } eleTimeSec.innerHTML=""};var timerTimeCount=null;var fnTimeCount=function(b){ if(timerTimeCount){ return } var b=b||10; var a=function(){ var c=b/10; if(eleCircles[1]){ eleCircles[1].setAttribute("stroke-dasharray",perimeter*c+" 1069") } if(eleCircles[2]&&b< =5){ eleCircles[2].setAttribute("stroke-dasharray",perimeter*c+" 1069") } if(eleTimeSec){ eleTimeSec.innerHTML=b } b--; if(b< 0){ clearInterval(timerTimeCount); timerTimeCount=null; alert("时间到！"); circleInit() } }; a(); timerTimeCount=setInterval(a,1000)};fnTimeCount();整个案例的代码非常少，有喜欢的朋友可以将代码保存到html中，运行一下，体验体验实际效果。
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