js 读秒

<input type="button" value="&nbsp;获取验证码&nbsp;" class="verification right" ">

$(".verification").click(function(){
var nums = 20;
var tel = $("#tel").val();
if(!is_mobile(tel)){
hint_msg('手机号码不正确');
return;
}else{
$(".verification").css('border','1px solid #B7B2B2').css("background-color","#B7B2B2").prop('disabled',true);
$(".verification").val(" "+nums+'秒后重试'+" ");
var timer = setInterval(Byoyomi,1000);
function Byoyomi() {
nums--;
if (nums > 0) {
$(".verification").val(" "+nums+'秒后重试'+" ");
} else {
clearInterval(timer); //清除js定时器
$(".verification").css('background-color','#FF8000').css('border','1px solid #FF8000').prop('disabled',false);
$(".verification").val(" "+"获取验证码"+" ");
nums = 20; //重置时间
}
}
}
});