Reducer Array CRUD

updateList.ts

/**
 * Returns a new list, based on the previous list.
 * Action describes how to create the new list.
 * Shallow Copy
 */
export function updateList(prevList: objectList, action: KeywordDispatchAction): objectList {
  const { type, listIndex, data } = action;
  // console.group('Action', type);

  switch (type) {
    case ACTION.create:
      return prevList.concat(data);
    case ACTION.update:
      if (listIndex == null) { throw new Error(`Update on list "${action.listName}" requested, but listIndex "${listIndex}" is an invalid index.`); }
      return prevList.map((item, index) => {
        if (index !== listIndex) {
          return item;
        }
        return Object.assign({}, item, data);
      });
    case ACTION.delete:
      if (listIndex == null) { throw new Error(`Update on list "${action.listName}" requested, but listIndex "${listIndex}" is an invalid index.`); }
      return prevList.filter((_, index) => index !== listIndex);
    default:
      return prevList;
  }
}