获取验证码按钮点击后，一分钟内不可继续点击

 1 <input type="button" id="btn" value="免费获取验证码" />
 2 <script type="text/javascript">
 3     var wait=60;
 4     function time(o) {
 5         if (wait == 0) {
 6             o.removeAttribute("disabled");
 7             o.value="免费获取验证码";
 8             wait = 60;
 9         } else {
10             o.setAttribute("disabled", true);
11             o.value="重新发送(" + wait + ")";
12             wait--;
13             setTimeout(function() {
14                 time(o)
15             },
16             1000)
17         }
18     }
19     document.getElementById("btn").onclick=function()
20     {time(this);}
21 </script>