jquery.countdown.js

(function($){
    function time_to_hms (time) {
        var amounts = {
            hours: 60*60,
            minutes: 60,
            seconds: 1
        },
        hms = [],
        unit = '',
        amount = '',
        scale = 1;
        
        for (unit in amounts) {
            scale = amounts[unit];
            amount = Math.floor(time/scale);
            time -= amount*scale;
            
            hms.push(amount.toString().replace(/^(\d)$/,'0$1'));
        }
        
        return hms.join(':');
    }
    
    function hms_to_time (hms) {
        var values;
        
        if (hms.match(/\d+:\d+:\d+/)) {
            values = hms.replace(/[\s\S]*?(\d+:\d+:\d+)[\s\S]*/,'$1').split(':');
            return (parseInt(values[0])*60 + parseInt(values[1]))*60 + parseInt(values[2]);
        }
        
        if (hms.match(/\d+:\d+/)) {
            values = hms.replace(/[\s\S]*?(\d+:\d+)[\s\S]*/,'$1').split(':');
            return parseInt(values[0])*60 + parseInt(values[1]);
        }
        
        if (hms.match(/\d+/)) {
            return parseInt(hms.replace(/[\s\S]*?(\d+)[\s\S]*/,'$1'));
        }
        
        return 0;
    }
    
    var methods = {
        init: function (options) {
            return this.each(function(){
                var $this = $(this),
                settings = {
                    time: false,
                    tick: 1,
                    start: function(target,settings){
                        return settings;
                    },
                    update: function(target,settings,remaining){},
                    done: function(target,settings){}
                },
                modified;
                
                if (options) {
                    $.extend(settings, options);
                }
                
                modified = settings.start($this,settings);
                settings = modified || settings;
                
                if (settings.time === false) {
                    settings.time = hms_to_time($this.text());
                }
                
                settings.limit = Math.floor((new Date()).getTime()/1000) + settings.time;
                
                settings.step = function(){
                    var remaining  = settings.limit - Math.floor((new Date()).getTime()/1000);
                    remaining = remaining <= 0 ? 0 : remaining;
                    
                    $this.text(time_to_hms(remaining));
                    settings.update($this,settings,remaining);
                    
                    if (!remaining) {
                        clearInterval(settings.interval);
                        settings.done($this,settings);
                    }
                };
                
                settings.interval = setInterval(settings.step,Math.floor(settings.tick*1000 - 5));
                settings.step();
            });
        }
    };
    
    $.fn.countdown = function (method) {
        if (methods[method]) {
            return methods[method].apply(this,Array.prototype.slice.call(arguments,1));
        }
        else if (typeof method === 'object' || ! method) {
            return methods.init.apply(this,arguments);
        }
        else {
            $.error('Method ' +  method + ' does not exist on jQuery.countdown');
        }
    };
})(jQuery);