Get parameter with key from express request context, a decorator function of value can be pass.

params.js

/**
 * Wrap express.request.param with decorator.
 *
 * @param {HttpRequest} req
 * @param {String} name
 * @param {Function} [decorator]
 * @param {Mixed} [defaultValue]
 * @returns value of parameter
 */

function param(req, name, decorator, defaultValue) {
	var v = req.param(name, defaultValue);
	return 'function' == typeof(decorator) ? decorator(v) : v;
}