@wordpress/preferences/build-module/store/reducer.js

Utilities for managing WordPress preferences.

/**
 * WordPress dependencies
 */
import { combineReducers } from '@wordpress/data';

/**
 * Reducer returning the defaults for user preferences.
 *
 * This is kept intentionally separate from the preferences
 * themselves so that defaults are not persisted.
 *
 * @param {Object} state  Current state.
 * @param {Object} action Dispatched action.
 *
 * @return {Object} Updated state.
 */
export function defaults(state = {}, action) {
  if (action.type === 'SET_PREFERENCE_DEFAULTS') {
    const {
      scope,
      defaults: values
    } = action;
    return {
      ...state,
      [scope]: {
        ...state[scope],
        ...values
      }
    };
  }
  return state;
}

/**
 * Higher order reducer that does the following:
 * - Merges any data from the persistence layer into the state when the
 *   `SET_PERSISTENCE_LAYER` action is received.
 * - Passes any preferences changes to the persistence layer.
 *
 * @param {Function} reducer The preferences reducer.
 *
 * @return {Function} The enhanced reducer.
 */
function withPersistenceLayer(reducer) {
  let persistenceLayer;
  return (state, action) => {
    // Setup the persistence layer, and return the persisted data
    // as the state.
    if (action.type === 'SET_PERSISTENCE_LAYER') {
      const {
        persistenceLayer: persistence,
        persistedData
      } = action;
      persistenceLayer = persistence;
      return persistedData;
    }
    const nextState = reducer(state, action);
    if (action.type === 'SET_PREFERENCE_VALUE') {
      persistenceLayer?.set(nextState);
    }
    return nextState;
  };
}

/**
 * Reducer returning the user preferences.
 *
 * @param {Object} state  Current state.
 * @param {Object} action Dispatched action.
 *
 * @return {Object} Updated state.
 */
export const preferences = withPersistenceLayer((state = {}, action) => {
  if (action.type === 'SET_PREFERENCE_VALUE') {
    const {
      scope,
      name,
      value
    } = action;
    return {
      ...state,
      [scope]: {
        ...state[scope],
        [name]: value
      }
    };
  }
  return state;
});
export default combineReducers({
  defaults,
  preferences
});
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