var _getType = function( inp ) {
        var type = typeof inp, match;
        var key;
        if (type == 'object' && !inp) {
            return 'null';
        }
        if (type == "object") {
            if (!inp.constructor) {
                return 'object';
            }
            var cons = inp.constructor.toString();
            if (match = cons.match(/(\w+)\(/)) {
                cons = match[1].toLowerCase();
            }
            var types = ["boolean", "number", "string", "array"];
            for (key in types) {
                if (cons == types[key]) {
                    type = types[key];
                    break;
                }
            }
        }
        return type;
    };

La verdad es que es bastante útil