DraftJS-pagination-complete.js

import { EditorState, ContentState, convertFromRaw } from 'draft-js';

const editorStateReducer = (state = defaultEditorState, action) => {
  switch(action.type) {  
    case MORE_CONTENT_RETRIEVED: {
      // Capture current state
      const currentContentState = state.getCurrentContent();
      const currentBlockMap = currentContentState.getBlockMap();
      const currentSelection = state.getSelection();

      // Create new ContentBlocks
      const { blocks } = action.payload;
      const newContentState = convertFromRaw({ blocks, entityMap: {} });
      const newBlockMap = newContentState.getBlockMap();

      // Combine new and existing ContentBlocks
      const combinedBlockMap = newBlockMap.concat(currentBlockMap);
      const combinedContentState = ContentState.createFromBlockArray(combinedBlockMap.toArray());
      
      // Push EditorState while excluding changes from undo/redo stack
      const stateNoUndo = EditorState.set(state, { allowUndo: false });
      const newState = EditorState.push(stateNoUndo, combinedContentState, 'insert-fragment');
      const stateAllowUndo = EditorState.set(newState, { allowUndo: true });
      
      // Maintain SelectionState
      const newStateWithSelection = EditorState.forceSelection(stateAllowUndo, currentSelection);
      
      // Return combined selection state
      return newStateWithSelection; 
    }
  }
}