<input type="button" id="btn" value="免费获取验证码" onclick="mbtime(this)"/>
<script type="text/javascript">
var wait=60;
function mbtime(o) {
	if (wait == 60) {
		//ajax发送短信
	}
	if (wait == 0) {
		o.removeAttribute("disabled");          
		o.value="获取手机校验码";
		wait = 60;
	} else {
		o.setAttribute("disabled", true);
		o.value="重新发送(" + wait + ")";
		wait--;
		setTimeout(function() {time(o)},1000)
	}
}
</script>