js时间，倒计时，格式化

// 2小时倒计时
function clock (time, fmt) {
    let h = Math.floor(time / (60 * 60));
    let hRemain = time % (60 * 60);
    let m = Math.floor(hRemain / 60);
    let mRemain = hRemain % 60;
    let s = mRemain;

    let obj = {
        "h+": ('00' + h).substr(-2),
        "m+": ('00' + m).substr(-2),
        "s+": ('00' + s).substr(-2),
    }

    for (let key in obj) {
        let pat = `(${key})`
        if (new RegExp(pat).test(fmt)) {
            let str = obj[key] + '';
            // RegExp.$1 hh mm ss贪婪匹配
            fmt = fmt.replace(RegExp.$1, str)
        }
    }
    return fmt;
}

let time = clock(3712, 'hh:mm:ss')
console.log(time)

• 留存备用
• 配上倒计时

let count = 722
setInterval(() => {
    if (!count) {
        return ;
    }
    let time = clock(count, 'hh:mm:ss')
    console.log(time)
    count--
}, 10);