为 Date 对象添加 ago 属性

/*
* 此处，__defineGetter__与__defineSetter__相当于C#实体中类中的get与set
**/
Date.prototype.__defineGetter__('ago',function () {
        var diff = ((new Date()).getTime() - this.getTime()) / 1000,
            day_diff = Math.floor(diff / 86400);
        return day_diff == 0 &&
                        diff < 60 && 'just now' ||
                        diff < 120 && '1 minute ago' ||
                        diff < 3600 && Math.floor( diff / 60 ) + 'minutes ago' ||
                        diff < 7200 && '1 hour ago' ||
                        day_diff == 1 && 'yesterday' ||
                        day_diff < 7 && day_diff + 'days ago' ||
                        Math.ceil( day_diff / 7 ) + 'weeks ago';

    });

测试一下

var a = new Date('12/12/1990')
a.ago// "1353weeks ago"

var a = new Date('2016-11-9')
a.ago// "yesterday"

var a = new Date('2016-11-5')
a.ago// "5days ago"

今后就根据需求变动其return的条件即可