merge only an object's properties into target that are defined in a given array.

merge.js

define('helpers/merge', function() {

    /**
     * Extend method. Deep cloning.
     * @param  {Object} target Object to be extended.
     * @return {Object}        Extended object.
     */
    var _merge = function merge(target, attributes) {

        var sources = [].slice.call(arguments, 2);

        var skip = buildCheck(attributes);

        sources.forEach(function(source) {
            for (var property in source) {

                if (skip(property)) continue;

                if (source[property] && source[property].constructor &&
                    source[property].constructor === Object) {
                    target[property] = target[property] || {};
                    target[property] = merge(target[property], source[property]);
                } else target[property] = source[property];
            }
        });

        return target;
    };

    function buildCheck(attributes) {

        if (typeof attributes === 'function') return attributes;

        if (Array.isArray(attributes)) {
            return function(attribute) {
                return attributes.indexOf(attribute) === -1;
            }
        }

        if (typeof attributes === 'boolean') return function(attribute) {
            return !attributes;
        }

        if (!attributes) return function(attribute) {
            return false;
        }
    }

    return _merge;
});

/*
 * Shim dependency.
 */
if (!Array.isArray) {
    Array.isArray = function(arg) {
        return Object.prototype.toString.call(arg) === '[object Array]';
    };
}