Beefed up javascript _namespace function

/**
 * Created by edelacruz on 2/17/14.
 */
(function (context) {
    /**
     * Takes a namespace string and fetches that location out from
     * an object/Map.  If the namespace doesn't exists it is created then
     * returned.
     * Example: _namespace('hello.world.how.are.you.doing', obj) will
     * create/fetch within `obj`:
     * hello: { world: { how: { are: { you: { doing: {} } } } } }
     * @param ns_string {String} the namespace you wish to fetch
     * @param objToSearch {Object} object to search for namespace on
     * @param valueToSet {Object} optional, a value to set on the key
     *  (last key if key string (a.b.c.d = value))
     * @param createEs6 {Boolean} optional, default `false` set undefined
     *  parts of `ns_string` in search with an es6 collection (only maps allowed at the
     *  moment as maps are the only es6 realistic use cases for _namespacing).
     * @returns {Object}
     */
    context._namespace = function (ns_string, objToSearch, valueToSet, createEs6) {
        createEs6 = createEs6 || false;

        var parts = ns_string.split('.'),
            parent = objToSearch,
            shouldSetValue = classOfIs(valueToSet, 'Undefined')
                ? false : true;
        i;

        for (i = 0; i < parts.length; i += 1) {
            // Traverse es6 collections (only maps currently supported)
            if (classOfIs(parent, 'Map')) {

                // If part not set set it
                if (!parent.has(parts[i])) {
                    var newObj = createEs6 && !shouldSetValue ? new Map() :
                        (shouldSetValue ? valueToSet : {});
                    parent.set(parts[i], newObj);
                    parent = newObj;
                }
                // If part is set
                else {
                    // Set value if necessary
                    if (shouldSetValue) {
                        parent.set(parts[i], valueToSet);
                    }
                    parent = parent.get(parts[i]);
                }
            }
            // Assume parent is an {Object}
            else {
                if (classOfIs(parent[parts[i]], 'Undefined')) {
                    parent[parts[i]] = {};
                }
                if (i === parts.length - 1 && shouldSetValue) {
                    parent[parts[i]] = valueToSet;
                }
                parent = parent[parts[i]];
            }
        };
    };

})(typeof window !== "undefined" ? window : global);