$(‘.btn‘).click(function(){
    var newTime = 60;
    var time = function(){
        newTime--;
        $(‘.btn‘).val(+newTime+"秒");
        if(newTime == 0){
            clearInterval(timer);
            $(‘.btn‘).val("重新获取");
        }
    }
    time();
    var timer = setInterval(time,100);
})

倒计时