js某一时间加上指定时长

function timeFormatter(d) {
        var d = new Date(d.substring(0, 4),
        d.substring(5, 7) - 1,
        d.substring(8, 10),
        d.substring(11, 13),
        d.substring(14, 16),
        d.substring(17, 19));
        d.setTime(d.getTime() + 5 * 1000);

        return d.getFullYear() + "-"
            + ((d.getMonth() + 1)<10?"0"+(d.getMonth() + 1):(d.getMonth() + 1))
            + "-" + (d.getDate() < 10 ? "0" + d.getDate() : d.getDate())
            + " " + (d.getHours()<10?"0"+d.getHours():d.getHours())
            + ":" + (d.getMinutes() < 10 ? "0" + d.getMinutes() : d.getMinutes())
            + ":" + (d.getSeconds() < 10 ? "0" + d.getSeconds() : d.getSeconds());
    } 

var second=timeFormatter('2017-08-04 23:59:55');console.log(second);         //2017-08-05 00:00:00

以上代码表示给定时间加上5秒。可以根据需要将5*1000变成指定时长，注定，单位是毫秒，返回的是结果字符串