JavaScript实现短信验证码发送倒计时功能

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
手机号码：<input type="text"><button>发送验证码</button>
<script>
  var btn=document.querySelector('button')
  var time=3
  btn.addEventListener('click',function () {
    btn.disabled=true
    var timer=setInterval(function () {
      if (time<0){
        clearInterval(timer)
        btn.disabled=false
        btn.innerHTML='发送验证码'
        time=3
      }else {
        btn.innerHTML = '还剩' + time + '秒'
        time -= 1
      }
    },1000)
  })
</script>
</body>
</html>