按钮不可用倒计时

//btn：当前按钮

function (btn){
var time = 60; //60秒
var counttime = setInterval(function () {
if (time > 0) {
$(btn).val(time-- + "秒后可重新发送")
}
else {
counttime = window.clearInterval(counttime);
$(btn).attr("disabled", false).val("确定").removeClass("btn-disable");
}
}, 1000);
}