redux-conditional/src/index.js

Make sharing reducers easy by conditionally applying actions to shared Redux reducers.

import {
  conditionalDefaultSubKey,
  simpleConditional,
} from './simpleConditional';

const unknownAction = { type: Symbol('REDUX CONDITIONAL UNKNOWN TYPE') };

const conditionalReducer = (conditionFn, reducer) => (state, action) => (
  reducer(state, conditionFn(state, action) ? action : unknownAction)
);

const normalizeTargets = (targets, conditionFnMaker) => {
  if (Array.isArray(targets)) {
    return targets.map(key => ({ key, conditionFn: conditionFnMaker(key) }));
  }

  return Object.keys(targets).map(key => ({ key, conditionFn: conditionFnMaker(targets[key]) }));
};

// simpleConditional().default expects the "data" can be accessed by action[conditionalKey][conditionalDefaultSubKey]
const conditionalReducerByKey = (targets, { conditionMaker } = simpleConditional().default) => {
  const normalized = normalizeTargets(targets, conditionMaker);

  return reducer => (state, action) => {
    const nextState = {};
    let changed = false;

    normalized.forEach((target) => {

      let subState = state;
      if (state) {
        subState = state[target.key];
      }

      nextState[target.key] = conditionalReducer(target.conditionFn, reducer)(subState, action);
      changed = changed || nextState[target.key] !== subState;
    });

    return changed ? nextState : state;
  };
};

export {
  conditionalReducer,
  conditionalReducerByKey,

  conditionalDefaultSubKey,
  simpleConditional,
};