计时器

var hour=0,min=0,second=0;

                setInterval(function(){

                    second++;

                    if(second==60){

                        second=0;

                        min++;

                    }

                    if(min==60){

                        min=0;

                        hour++

                    }

                    $("#tt").html((hour<10?"0":"") +hour+":"+(min<10?"0":"")+min+":"+(second<10?"0":"")+second)

                },1000)