functional javascript - recursively walking a tree to build up a new one; could this be better factored as a reduce?

gistfile1.js

/**
 * recursively build a nested Backbone.Model or Backbone.Collection
 * from a deep JSON structure.
 *
 * undefined for regex values
 */
exports.modelify = function modelify (data) {

    if (_.isArray(data)) {
        return new Backbone.Collection(_.map(data, modelify));
    }

    else if (_.isObject(data) && !_.isDate(data)) {

        var m = util.mapo(data, function(val, key) {
            return [key, modelify(val)];
        });

        return new Backbone.Model(m);
    }
    else {
        // data is a primitive or a date
        return data;
    }
}

var mapo = exports.mapo = _.compose(_.object, _.map);