js 日期+分钟+秒 倒计时

function ShowCountDown() {

    var now = new Date();

    var endDate = new Date("2015/09/20 15:11:00");
4000
//可更改

    var leftTime = endDate.getTime() - now.getTime();

    console.log();

    var leftsecond = parseInt(leftTime / 1000);

    var day1 = Math.floor(leftsecond / (60 * 60 * 24));

    var hour = Math.floor((leftsecond - day1 * 24 * 60 * 60) / 3600);

    var minute = Math.floor((leftsecond - day1 * 24 * 60 * 60 - hour * 3600) / 60);

    var second = Math.floor(leftsecond - day1 * 24 * 60 * 60 - hour * 3600 - minute * 60);

    if (day1 < 10) {

        day1 = "0" + day1;

    }

    if (hour < 10) {

        hour = "0" + hour;

    }

    if (minute < 10) {

        minute = "0" + minute;

    }

    var dayId = document.getElementById("day");

    var hourId = document.getElementById("hour");

    var minId = document.getElementById("min");

    dayId.innerHTML = day1;

    hourId.innerHTML = hour;

    minId.innerHTML = minute;

}

window.setInterval(function() {

    ShowCountDown();

},

1000);