JavaScript lists

lists.js

// convert from array to list with
function arrayToList(arr) {
  // list format: value 1, rest => value 2, rest => value 3, rest => null
  let list;
  for (let i = arr.length; i >= 0; i--) {
    list = {
      value: arr[i],
      rest: i >= arr.length - 1 ? null : list,
    };
  }
  return list;
}

// convert from list to array with
function listToArray(list) {
  const arr = [];

  for (let node = list; node; node = node.rest) {
    arr.push(node.value);
  }

  return arr;
}

// prepend to list with
function prepend(element, list) {
  let count = 0;
  for (let node = list; node; node = node.rest) {
    if (count === 0) {
      list = {
        value: element,
        rest: list,
      };
    }
    count++;
  }

  return list;
}

// find nth (zero-based) value in list with
function nth(list, number) {
  let count = 0;
  let result;

  for (let node = list; node; node = node.rest) {
    if (count === number) {
      res = node;
    }
    count++;
  }

  return result;
}