Delete an item from Redux state

Just filter the comments:

case 'DELETE_COMMENT':
  const commentId = action.data;
  return state.filter(comment => comment.id !== commentId);

This way you won't mutate the original state array, but return a new array without the element, which had the id commentId.

To be more concise:

case 'DELETE_COMMENT':
  return state.filter(({ id }) => id !== action.data);

You can use Object.assign(target, ...sources) and spread all the items that don't match the action id

case "REMOVE_ITEM": {
  return Object.assign({}, state, {
    items: [...state.items.filter(item => item.id !== action.id)],
  });
}

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