图（1）初始图
图（2）点击后
代码如下：
<!DOCTYPE HTML> <html> <head> <meta charset="UTF-8" /> <title>pro.html</title> <style type="text/css"> .checkCode { cursor: pointer; border: 1px solid black; text-align: center; line-height: 26px; width: 115px; height: 35px; } </style> <script type="text/javascript"> var sleep = 30, interval = null; window.onload = function () { var btn = document.getElementById ('btn'); btn.onclick = function () { if (!interval) { this.style.backgroundColor = 'rgb(243, 182, 182)'; this.disabled = "disabled"; this.style.cursor = "wait"; this.value = "重新发送 (" + sleep-- + ")"; interval = setInterval (function () { if (sleep == 0) { if (!!interval) { clearInterval (interval); interval = null; sleep = 30; btn.style.cursor = "pointer"; btn.removeAttribute ('disabled'); btn.value = "免费获取验证码"; btn.style.backgroundColor = ''; } return false; } btn.value = "重新发送 (" + sleep-- + ")"; }, 1000); } } } </script> </head> <body> <input type="button" value="免费获取验证码" /> </body> </html>