console 命令行工具 X clear

console

var count = 0;
var interval = null;
document.getElementById("begin").addEventListener("click", function(){
  interval = setInterval(function(){
    document.getElementById("count").innerText = count++;
  }, 8)
})

document.getElementById("end").addEventListener("click", function(){
  clearInterval(interval);
  interval = null;
})

<div id="begin">开始</div>
<div id="end">结束</div>
<div id="count"></div>

#count{
  color:red;
  font-size:200px;
}
#begin,#end{
  display:inline-block;
  margin:0 10px;
}