index.js

var arr = "2021-01-01 00:06:00".split(/[- :]/);//改这里
var box = document.getElementsByClassName('textCon')[0];
function init() {
    var width = box.offsetWidth;
    var count = parseInt(width / 50 * 5);
    for (var i = 0; i < count; i++) {
        var size = parseInt(ran(60, 120) / 10);
        var ele = document.createElement('div');
        ele.classList.add('item');
        ele.style.width = size + 'px';
        ele.style.height = size + 'px';
        ele.style.left = ran(0, 95) + '%';
        ele.style.top = ran(20, 80) + '%';
        ele.style.animationDelay = ran(0, 30) / 10 + 's';
        box.appendChild(ele);
    }
}
function ran(min, max) {
    min = parseInt(min);
    max = parseInt(max);
    return Math.floor(Math.random() * (max - min + 1)) + min;
}
function timer_start(){

    var start_time = new Date(arr[0], arr[1]-1, arr[2], arr[3], arr[4], arr[5]);
    // var start_time =  new Date(beginTime);
    // var start_time = Date.parse(beginTime);
    var duration = parseInt(new Date()- start_time)/1000;
    var seconds = parseInt( duration % 60);
    if (seconds < 10)
        seconds = "0" + seconds;
    duration = parseInt(duration / 60);
    var minutes = duration % 60;
    if (minutes < 10)
        minutes = "0" + minutes;
    duration = parseInt(duration / 60);
    var hours = duration % 24;
    if (hours < 10)
        hours = "0" + hours;
    duration = parseInt(duration / 24);
    var days = duration;
    document.getElementsByClassName('days-number')[0].innerHTML = ("" +days);
    document.getElementsByClassName('seconds')[0].innerHTML = (hours + " 时 " + minutes + " 分 " + seconds + " 秒");
}
window.setInterval(timer_start,1000);
timer_start();
init();