harness/app-assets/templates/assets/js/modules/relativeDates.js

/*global define */
define(function() {
    'use strict';

    function isToday(date) {
        var today = new Date();

        return (date.toDateString() === today.toDateString());
    }

    function isWithin24Hours(date) {
        var today = new Date();

        return (date.valueOf() > (today.valueOf() - (24 * 60 * 60 * 1000)));
    }

    function isWithinPastWeek(date) {
        var daysAgo = new Date().valueOf() - (7 * 24 * 60 * 60 * 1000);
        return date.valueOf() >= daysAgo;
    }

    function isWithinPastYear(date) {
        var weeksAgo = new Date().valueOf() - (52 * 7 * 24 * 60 * 60 * 1000);
        return date.valueOf() >= weeksAgo;
    }

    function isValidDate(date) {
        if (Object.prototype.toString.call(date) !== '[object Date]') {
            return false;
        }
        return !isNaN(date.getTime());
    }

    function makeRelativeDate(epoch) {
        var then = new Date(Number(epoch)),
            now = new Date(),
            delta;

        if (!isValidDate(then)) {
            return false;
        }

        delta = parseInt((now.getTime() - then) / 1000, 10);

        if (delta < 0) {
            return false;
        } else if (delta < 55) {
            return delta + 's';
        } else if (delta < (55 * 60)) {
            var minutesAgo = Math.round(delta / 60, 10);

            if (minutesAgo === 1) {
                return 'Now';
            } else {
                return (minutesAgo) + 'm ago';
            }
        } else if (isToday(then) || isWithin24Hours(then)) {
            var hoursAgo = Math.round(delta / 3600);

            return (hoursAgo) + 'h ago';
        } else if (isWithinPastWeek(then)) {
            var daysAgo = Math.round(delta / 3600 / 24);

            return (daysAgo) + 'd ago';
        } else if (isWithinPastYear(then)) {
            var weeksAgo = Math.round(delta / 3600 / 24 / 7);

            return (weeksAgo) + 'w ago';
        } else {
            var yearsAgo = Math.round(delta / 3600 / 24 / 7 / 52);

            return (yearsAgo) + 'y ago';
        }
    }

    function replaceValidTimestamps(selector, attr) {
        var datetime,
            elem,
            elems,
            i,
            relativeDate,
            targetEl;

        elems = document.querySelectorAll(selector + '[' + attr + ']');

        for (i = 0; i < elems.length; i++) {
            elem = elems[i];
            datetime = new Date(elem.getAttribute(attr));
            relativeDate = makeRelativeDate(datetime.getTime());

            if (relativeDate) {
                targetEl = elem.getElementsByClassName('timestamp__text')[0] || elem;

                if (!targetEl.getAttribute('title')) {
                    targetEl.setAttribute('title', targetEl.innerText);
                }

                targetEl.innerHTML = relativeDate;
            }
        }
    }

    function init(selector, attr) {
        replaceValidTimestamps(selector, attr);
    }

    return {
        init: init
    };

});