_niceDate.js

// http://d.hatena.ne.jp/piglovesyou/20111105/1320516029
// depends on underscore.js
// @param {String|Number|Date} date
// @param {?String=} lang 'ja' or 'en'. default is 'ja'
// @return {String}
_.mixin({
    niceDate: (function(date, lang) {
        var DAY, HOUR, MINUTE, MONTH, SECOND, WEEK, YEAR, dateFormat, formatize, langs, pluralize;
        SECOND = 1000;
        MINUTE = 60 * SECOND;
        HOUR = 60 * MINUTE;
        DAY = 24 * HOUR;
        WEEK = 7 * DAY;
        MONTH = 31 * DAY;
        YEAR = 365 * DAY;
        langs = {
            en: {
                AGO: ' ago',
                AFTER: ' after',
                SECOND: ' second',
                MINUTE: ' minute',
                HOUR: ' hour',
                DAY: ' day',
                WEEK: ' week',
                MONTH: ' month',
                YEAR: ' year',
                PLURAL: 's'
            },
            ja: {
                AGO: '前',
                AFTER: '後',
                SECOND: '秒',
                MINUTE: '分',
                HOUR: '時間',
                DAY: '日',
                WEEK: '週',
                MONTH: '月',
                YEAR: '年'
            }
        };
        dateFormat = {
            en: {
                HOUR_MINUTE: "%_:%_",
                MONTH_DATE: "%_.%_",
                YEAR_MONTH_DATE: "%_.%_.%_"
            },
            ja: {
                HOUR_MINUTE: "%_:%_",
                MONTH_DATE: ["%_", langs.ja.MONTH, "%_", langs.ja.DAY].join(''),
                YEAR_MONTH_DATE: ["%_", langs.ja.YEAR, "%_", langs.ja.MONTH, "%_", langs.ja.DAY].join('')
            }
        };
        pluralize = function(num, str, lang) {
            num = Math.floor(num);
            if (lang.PLURAL && num > 1) {
                return num + str + lang.PLURAL;
            } else {
                return num + str;
            }
        };
        formatize = function() {
            var format, value, values, _i, _len;
            var __slice = Array.prototype.slice;
            format = arguments[0], values = 2 <= arguments.length ? __slice.call(arguments, 1) : [];
            for (_i = 0, _len = values.length; _i < _len; _i++) {
                value = values[_i];
                format = format.replace("%_", value);
            }
            return format;
        };
        return function(date, lang_) {
            var agoOrLater, dist, fmt, now;
            if (_.isString(date) || _.isNumber(date)) {
                date = new Date(date);
            }
            if (_.isDate(date)) {
                now = new Date().getTime();
                lang_ = _.isString(lang_) && langs[lang_] ? lang_ : "ja";
                lang = langs[lang_];
                fmt = dateFormat[lang_];
                dist = now - date.getTime();
                agoOrLater = dist > 0 ? lang.AGO : lang.AFTER;
                dist = Math.abs(dist);
                if (dist < MINUTE) {
                    return "" + (pluralize(dist / SECOND, lang.SECOND, lang)) + agoOrLater;
                } else if (dist < HOUR) {
                    return "" + (pluralize(dist / MINUTE, lang.MINUTE, lang)) + agoOrLater;
                } else if (dist < DAY) {
                    return "" + (pluralize(dist / HOUR, lang.HOUR, lang)) + agoOrLater;
                } else if (dist < DAY * 356) {
                    return "" + (pluralize(dist / DAY, lang.DAY, lang)) + agoOrLater;
                } else if (dist < YEAR) {
                    return "" + (formatize(fmt.MONTH_DATE, date.getMonth() + 1, date.getDate()));
                } else {
                    return "" + (formatize(fmt.YEAR_MONTH_DATE, date.getFullYear(), date.getMonth() + 1, date.getDate()));
                }
            }
        };
    })()
});