Love short code contests!

function SinceWhen(receivedDate, currentDate, language) {
    const ONE_SECOND = 1000;
    const ONE_MINUTE = ONE_SECOND * 60;
    const ONE_HOUR = ONE_MINUTE * 60;
    const ONE_DAY = ONE_HOUR * 24;

    const SECOND_EN = "second";
    const MINUTE_EN = "minute";
    const HOUR_EN = "hour";
    const DAY_EN = "day";
    const NOW_EN = "Just now";
    const YESTERDAY_EN = "Yesterday";

    const SECOND_FR = "seconde";
    const MINUTE_FR = "minute";
    const HOUR_FR = "heure";
    const DAY_FR = "jour";
    const NOW_FR = "à l'instant";
    const YESTERDAY_FR = "hier";

    var junk
    , ms = currentDate - receivedDate;
    , elapsedDays    = parseInt(ms / ONE_DAY,10)
    , elapsedHours   = parseInt(ms / ONE_HOUR,10)
    , elapsedMinutes = parseInt(ms / ONE_MINUTE, 10)
    , elapsedSeconds = parseInt(ms / ONE_SECOND, 10)
    ;

    return language == 1
        ? (elapsedDays > 0
            ? (elapsedDays === 1
              ? YESTERDAY_EN
              : getString(DAY_EN, elapsedDays, 1)
              )
            : (elapsedHours > 0
              ? getString(HOUR_EN, elapsedHours, 1)
              : (elapsedMinutes > 0
                ? getString(MINUTE_EN, elapsedMinutes, 1)
                : (elapsedSeconds > 10
                 ? getString(SECOND_EN, elapsedSeconds, 1)
                 : NOW_EN
                 )
                )
              )
            )
        : (elapsedDays > 0
            ? (elapsedDays === 1
              ? YESTERDAY_FR
              : getString(DAY_FR, elapsedDays)
              )
            : (elapsedHours > 0
              ? getString(HOUR_FR, elapsedHours)
              : (elapsedMinutes > 0
                ? getString(MINUTE_FR, elapsedMinutes)
                : (elapsedSeconds > 10
                 ? getString(SECOND_FR, elapsedSeconds)
                 : NOW_FR
                 )
                )
              )
            )
        ;
}

function getString(span, length, language) {
    return language == 1
        ? (length === 1
          ? "One " + span + " ago"
          : length + " " + span + "s ago"
          )
        : "Il y a " + (length === 1
          ? "un" + (span === 'DAY_FR' ? '' : 'e') + " " + span
          : length + " " + span + "s"
          )
        ;
}

>>Something is very slow here if I have about 200 items on the page. I would have expected that to slow around 40,000. Anyone would have an idea on how to optimize this logic to avoid this javascript latency?
>
>Seems to me you are doing some calculations unnecessarily (e.g current date every time, hours, minutes and seconds when only day is of interest). Also I think the calculations themselves could be simplified. This looks shorter:

function SinceWhen(receivedDate, currentDate, language) {
>            const ONE_SECOND = 1000;
>            const ONE_MINUTE = ONE_SECOND * 60;
>            const ONE_HOUR = ONE_MINUTE * 60;
>            const ONE_DAY = ONE_HOUR * 24;
>
>            const SECOND = "second";
>            const MINUTE = "minute";
>            const HOUR = "hour";
>            const DAY = "day";
>            const NOW = "Just now";
>            const YESTERDAY = "Yesterday";
>
>            var retstring = "";
>
>            var elapsedDays =  parseInt((currentDate - receivedDate) / ONE_DAY,10);
>            if (elapsedDays > 0) {
>                if (elapsedDays === 1){
>                    retstring = YESTERDAY;
>                } else {
>                    retString = getString(DAY, elapsedSeconds);
>                }
>            } else {
>                var elapsedHours = parseInt( (currentDate - receivedDate) / ONE_HOUR,10);
>                if (elapsedHours > 0) {
>                    retString = getString(HOUR, elapsedSeconds);
>                } else {
>                    var elapsedMinutes = parseInt((currentDate - receivedDate) / ONE_MINUTE, 10);
>                    if (elapsedMinutes > 0) {
>                        retString = getString(MINUTE, elapsedSeconds);
>                    } else {
>                        var elapsedSeconds = parseInt((currentDate - receivedDate) / ONE_SECOND, 10);
>                        if (elapsedSeconds < 10) {
>                            retstring = NOW
>                        } else {
>                            retString = getString(SECOND, elapsedSeconds);
>                        }
>                    }
>                }
>            }
>            return retstring;
>        }
>
>        function getString(span, length) {
>            if (length === 1) {
>                return "One " + span + " ago";
>            } else {
>                return length + " " + span + "s ago";
>            }
>        }

Not properly tested :-} Not dealing with the language issue (which could be handled in the getString() method) But I'm not sure it would improve performance - manipulating the DOM is probably taking most of the time.