gistfile1.js

function getFriends( userId, people ){
	var user, friendList, friendsIdList, friendsList = null;

	function checkUser( id ){
		return people[id]
	}

	function findPeople( id ){
		var foundPerson;
		people.forEach( function ( person ){
			if ( person.id === id ) foundPerson = person;
		} );
		return foundPerson;
	}

	function getFriendsIdList( user ){
		friendList = user ? user.friends : null;
		return friendList;
	}

	function getFriendsList( friendsList ){
		var _friends = [];
		var list = friendsList || [];
		_friends = list.map( findPeople );
		return _friends;
	}

	if ( checkUser( userId ) ) {
		user = findPeople( userId );
		friendsIdList = getFriendsIdList( user );
		friendsList = getFriendsList( friendsIdList );
	}

	return friendsList;
}