Sindbad~EG File Manager

    $.RangeMapClass = RangeMap = createClass({
        init: function (map) {
            var key, range, rangelist = [];
            for (key in map) {
                if (map.hasOwnProperty(key) && typeof key === 'string' && key.indexOf(':') > -1) {
                    range = key.split(':');
                    range[0] = range[0].length === 0 ? -Infinity : parseFloat(range[0]);
                    range[1] = range[1].length === 0 ? Infinity : parseFloat(range[1]);
                    range[2] = map[key];
                    rangelist.push(range);
                }
            }
            this.map = map;
            this.rangelist = rangelist || false;
        },

        get: function (value) {
            var rangelist = this.rangelist,
                i, range, result;
            if ((result = this.map[value]) !== undefined) {
                return result;
            }
            if (rangelist) {
                for (i = rangelist.length; i--;) {
                    range = rangelist[i];
                    if (range[0] <= value && range[1] >= value) {
                        return range[2];
                    }
                }
            }
            return undefined;
        }
    });

    // Convenience function
    $.range_map = function(map) {
        return new RangeMap(map);
    };