Remove element from a nested array without using Immutability Helper

Question

I have a state Object that looks like this:

//State Object
playlistDict: {
  someId1: {
    active: false,
    id: 'someId',
    name: 'someName',
    pages: [ 'pageId1', 'pageId2', 'pageId3', etc ]  // I want to remove an element from this array
  },
  someId2: {
    active: false,
    id: 'someId2',
    name: 'someName2',
    pages: [ 'pageId11', 'pageId22', 'pageId33', etc ] // I want to remove an element from this array
  }
}

I'm trying to write a reducer that removes a page element given the index to remove without using immutability helper.

This is what I'm trying to do but my syntax is off and I'm not sure what's the correct way to write the reducer:

export function _removePageFromPlaylist( playlistId, pageIndex ) {
  return { type: types.REMOVE_PAGE_FROM_PLAYLIST, playlistId, pageIndex };
}

case types.REMOVE_PAGE_FROM_PLAYLIST: {    
      let playlistCopy = Object.assign( {}, state.playlistDict[ action.playlistId ]);
      playlistCopy.pages = Object.assign( {}, state.playlistDict[ action.playlistId ].pages );
      playlistCopy.pages.splice( action.pageIndex, 1 );

      return Object.assign({}, state, {
        playlistDict: { ...state.playlistDict, playlistDict[ action.playlistId ]: playlistCopy }  // doesn't like this syntax in particular
      });
    }

EDIT: In regards to people thinking it's the same as my other question, I'm asking this question because I'm trying to figure out if my reducer USING immutability helper is messing up my Firebase database, so I'm trying to figure out how to write the reducer WITHOUT using immutability helper so i can help eliminate what my bug is.

Answer 1

Use spread operator, and write it like this:

case types.REMOVE_PAGE_FROM_PLAYLIST: {    
    let playlistCopy = [...(state.playlistDict[ action.playlistId ].pages)];
    playlistCopy.splice( action.pageIndex, 1 );

    return {
        ...state,
        playlistDict: {
            ...state.playlistDict,
            [action.playlistId]: {
                ...state.playlistDict[action.playlistId],
                pages: playlistCopy
            }
        }
    }
}

Answer 2

Using Object Spread Operator:

case types.REMOVE_PAGE_FROM_PLAYLIST: {
  return {
    ...state,
    playlistDict: {
      ...state.playlistDict,
      [action.playlistId]: {
        ...state.playlistDict[action.playlistId],
        pages: [...state.playlistDict[action.playlistId].pages].splice(action.pageIndex, 1)
      }
    }
  }
}