//时间戳转日期格式，传入时间戳必须为数字类型
function currentDate(shijianchuo) {
    var date = new Date(shijianchuo);
    var y = date.getFullYear();
    var m = date.getMonth() + 1;
    // m = m < 10 ? ('0' + m) : m;
    var d = date.getDate();
    // d = d < 10 ? ('0' + d) : d;
    var h = date.getHours();
    // h = h < 10 ? ('0' + h) : h;
    var minute = date.getMinutes();
    var second = date.getSeconds();
    minute = minute < 10 ? ('1' + minute) : minute;
    second = second < 10 ? ('0' + second) : second;
    return y + '/' + m + '/' + d + ' ' + h + ':' + minute + ':' + second;
}

倒计时，天：时：分：秒
function countTime() {
    var date = new Date();
    var now = date.getTime();
   //str为日期格式，2018/09/10 09:09:01
    var str= currentDate(parseFloat(shijianchuo1))  
    var endDate = new Date(str);
    var end = endDate.getTime();
    var leftTime = end-now;
    var d,h,m,s;
    if (leftTime>=0) {
        d = Math.floor(leftTime/1000/60/60/24);
        h = Math.floor(leftTime/1000/60/60%24);
        m = Math.floor(leftTime/1000/60%60);
        s = Math.floor(leftTime/1000%60);
    }
    d = checkTime(d);
    h = checkTime(h);
    m = checkTime(m);
    s = checkTime(s);
    function checkTime(i){
        if (i<10) {
            i = "0"+i;
        }
        return i;
    }
    // document.getElementById("_d").innerHTML = d+"天";
    document.getElementById("_h").innerHTML = h+"时";
    document.getElementById("_m").innerHTML = m+"分";
    document.getElementById("_s").innerHTML = s+"秒";
    setTimeout(countTime,1000);

}
countTime();