console 命令行工具 X clear

console

var countdown = 60;

function setTime(val) {
  if (countdown === 0) {
    val.removeAttribute("disabled");
    val.value = "免费获取验证码";
    countdown = 60;
  } else {
    val.setAttribute("disabled", true);
    val.value = "重新发送(" + countdown + ")";
    countdown--;
    setTimeout(function() {
      setTime(val)
    },
    1000)
  }
}

<input type="button" value="获取验证码" onclick="setTime(this)" />