35、实时更新日期

                <div class="header-date">
                    <div class="date-time" id="date-time"></div>
                    <div class="date-right">
                        <div class="date-date" id="date-date"></div>
                        <div class="date-week" id="date-week"></div>
                    </div>
                </div>

window.onload = function(){
    showDateTime()
    setInterval(() => {
        showDateTime()
    }, 1000);
}
function showDateTime() {
    var date = new Date()
    var y = date.getFullYear()
    var M = formatNum(date.getMonth() + 1)
    var d = formatNum(date.getDate())
    var h = formatNum(date.getHours())
    var m = formatNum(date.getMinutes())
    var s = formatNum(date.getSeconds())
    var w = date.getDay()
    var week = ['日', '一', '二', '三', '四', '五', '六']
    document.getElementById('date-time').innerHTML = `${h}:${m}:${s}`
    document.getElementById('date-date').innerHTML = `${y}-${M}-${d}`
    document.getElementById('date-week').innerHTML = `星期${week[w]}`
}
function formatNum(m) {
    return m < 10 ? `0${m}` : m
}