reusable custom events

events.js

var Events = function() {
    var events = {};
    return {
        on : function(event, callback) {
            events[event] = events[event] || [];
            events[event].push(callback);
            return this;
        },

        off : function(event, callback) {
            var callbacks;

            // if no arguments - remove all handlers
            if (!event) {
                events = {};
                return this;
            }

            callbacks = events[event];

            // nothing to remove
            if (!callbacks) {
                return this;
            }

            // if no callback remove all handlers
            if (!callback) {
                events[event] = [];
                return this;
            }

            //find and remove handler
            for (i = 0; i < callbacks.length; i++) {
                if (callbacks[i] === callback) {
                    events[event].splice(i, 1);
                    return this;
                }
            }
        },

        fire : function(event) {
            var i, n, args,
                callbacks = events[event];

            if (callbacks) {
                args = Array.prototype.slice.call(arguments, 1);
                for (i = 0, n = callbacks.length; i < n; i++) {
                    callbacks[i].apply(null, args);
                }
            }
            return this;
        }
    }
}