function fn(time) {

    var date = new Date(time);

    var len = time.toString().length;

    // 时间戳不足13位则在后面加零

    if (len < 13) {

        var sub = 13 - len;

        sub = Math.pow(10, sub);

        date = new Date(time * sub);

    }

    var y = date.getFullYear() + '-';

    var M = date.getMonth() + 1;

    M = (M < 10 ? '0' + M : M) + '-';

    var d = date.getDate();

    d = (d < 10 ? '0' + d : d) + ' ';

    var h = date.getHours();

    h = (h < 10 ? '0' + h : h) + ':';

    var m = date.getMinutes();

    m = (m < 10 ? '0' + m : m) + ':';

    var s = date.getSeconds();

    s = s < 10 ? '0' + s : s;

    return y + M + d + h + m + s;

}

console.log(fn(1557003785));  //2019-05-05 05:03:05