text: 
  var wait=60;
  function time(o) {
      if (wait == 0) {
          o.removeAttribute("disabled");
          o.value="免费获取验证码";
          o.css("color","red");
          wait = 60;
      } else {
          o.setAttribute("disabled", true);
          o.value=wait+"秒后可以重新发送";
          wait--;
          setTimeout(function() {
                  time(o)
              },
              1000)
      }
  }
  document.getElementById("btn").onclick=function(){time(this);}