日期格式化

Date.prototype.DateFormat = function (fmt) {
    fmt = fmt || "yyyy-MM-dd";

    const o = {
        "M+": this.getMonth() + 1,
        "d+": this.getDate(),
        "h+": this.getHours(),
        "m+": this.getMinutes(),
        "s+": this.getSeconds(),
        "q+": Math.floor((this.getMonth() + 3) / 3),
        "S": this.getMilliseconds()
    };
    if (/(y+)/.test(fmt)) {
        fmt = fmt.replace(RegExp.$1, (`${this.getFullYear()}`).substr(4 - RegExp.$1.length));
    }
    for (const k in o) {
        if (new RegExp(`(${k})`).test(fmt)) {
            fmt = fmt.replace(RegExp.$1, (RegExp.$1.length === 1) ? (o[k]) : ((`00${o[k]}`).substr((`${o[k]}`).length)));
        }
    }
    return fmt;
};