jQuery jAM, Season 6

	 
	 
function arrayToList(array){
	var list = null;
	for (var i = array.length-1; i >=0;i--)
	list ={value:array[i], rest:list};
	return list;
}

function listToArray(list){
	var array = [];
	for (var node = list; node; node = node.rest)
	array.push(node.value);
	return array;
}

function prepend(value,list){
	return {value: value, rest:list};
}

function nth(list, n){
	if(!list)
		return undefined;
	else if (n==0)
		return list.value;
	else
		return nth(list.rest, n-1);
}
console.log(arrayToList([10, 20]));
// → {value: 10, rest: {value: 20, rest: null}}
console.log(listToArray(arrayToList([10, 20, 30])));
// → [10, 20, 30]
console.log(prepend(10, prepend(20, null)));
// → {value: 10, rest: {value: 20, rest: null}}
console.log(nth(arrayToList([10, 20, 30]), 1));
// → 20