手机号码:<input type="number"> <button>发送</button>

<script>
  var btn = document.querySelector('button');
  var time=6;
 btn.addEventListener('click', function(){
    btn.disabled= true;
    var ttt=  setInterval( function(){
     if( time==0 ){clearInterval(ttt);time=6; btn.disabled= false; btn.innerHTML='发送';}
     else {btn.innerHTML="还剩下"+time+"秒"; time--;};
    },1000);
    
 });
</script>