/**
 * Extends a class with new methods and member properties.
 *
 * @ignore
 * @param {Function} Child function
 * @param {Object|Function} ParentOrPrototype class to inherit from
 *  OR if no inheriting class a prototype to extend the class with
 * @param {Object} [prototype]
 */
module.exports = function mfExtend( Child, ParentOrPrototype, prototype ) {
	let key;
	if ( prototype ) {
		OO.inheritClass( Child, ParentOrPrototype );
	} else {
		OO.initClass( Child );
		prototype = ParentOrPrototype;
	}
	for ( key in prototype ) {
		Child.prototype[key] = prototype[key];
	}
};