Get sorting of query.

sorting.js

/**
 * Get sorting of query.
 *
 * @param {HttpRequest} req
 * @param {Object} options
 *    	- {Boolean} [customizable]
 *			whether the sorting is customizable
 *			i.e. can be pass from query string with the key $sort
 *			e.g. $sort=id,-key
 *		- {String} [defaults]
 *			defined default sorting of query
 *			e.g. 'id -key'
 * @returns {String} sorting part for query
 */

function __sorting(req, options) {

	var result = null,
	    opt = options || {};

	// customizable
	if (opt.customizable) {
		result = utils.param(req, '$sort', function(value) {
			return value ? value.replace(/\,/g, ' ') : null;
		});
	};

	// default
	if (!result && opt.defaults) {
		result = opt.defaults;
	};

	return result;
}