Date.prototype.Format = function (fmt) { //author: meizz
    var o = {
        "M+": this.getMonth() + 1, //月份
        "d+": this.getDate(), //日
        "h+": this.getHours(), //小时
        "m+": this.getMinutes(), //分
        "s+": this.getSeconds(), //秒
        "q+": Math.floor((this.getMonth() + 3) / 3), //季度
        "S": this.getMilliseconds() //毫秒
    };
    if (/(y+)/.test(fmt)) fmt = fmt.replace(RegExp.$1, (this.getFullYear() + "").substr(4 - RegExp.$1.length));
    for (var 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;
}

function getDate(strDate) {
    var st = strDate;
    var a = st.split(" ");
    var b = a[0].split("-");
    var c = a[1].split(":");
    var date = new Date(b[0], b[1], b[2], c[0], c[1], c[2]);
    return date;
}


调用：

var olddate=getDate("2020-02-04 20:38:20");
var newdate=JSON.stringify(olddate.Format("yyyy年MM月dd hh:mm:ss"));