Meta charset="UTF-8"> var timerId = null; var btn = document.getElementById("btn"); var num = 5; btn.onclick = function () { btn.disabled = true; timerId = setInterval(function () { num--; btn.value = num + "秒后可以发送"; if (num === 0) { clearInterval(timerId); btn.value = "点击发送验证码"; btn.disabled = false; num = 5; } },1000); };