<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<style>
svg{
width: 500px;
height: 500px;
border:1px solid red;
}
#s line:nth-of-type(2){
stroke-dasharray: 100,100;
stroke-dashoffset: 100;
}
</style>
</head>
<body>
<svg id="s">
<line x1="0" y1="5" x2="100" y2="5" stroke="purple" stroke-width="10" />
<line x1="0" y1="5" x2="100" y2="5" stroke="red" stroke-width="10" />
</svg>
</body>
<script>
var l=document.querySelector("#s line:nth-of-type(2)");
var timer=null;
var i=100;
function fn(){
timer=requestAnimationFrame(function(){
i--;
l.style.strokeDashoffset=i;
console.log(i);
if(i>0){
fn();
}
})
}
fn();
</script>
</html>
