createSelectorSelector

createSelectorSelector.js

import { createSelector } from 'reselect';
import _ from 'underscore';

const createSelectorSelector = (...funcs) => {
  const base = createSelector(...funcs);
  const selector = (...args) => base(...args)(...args);
  _.extendOwn(selector, base);
  return selector;
};

export default createSelectorSelector;

createSelectorSelector.test.js

import createSelectorSelector from "./createSelectorSelector";

describe("createSelectorSelector", () => {
  it("efficiently recomputes", () => {
    var state = { choiceA: 'aaa', choiceB: 'bbb', choice: 'choiceA' };

    const getChoiceA = s => s.choiceA;
    const getChoiceB = s => s.choiceB;
    const getChoice = s => s.choice;

    const selector = createSelectorSelector(
      [ getChoice ],
      choice => {
        return choice == 'choiceA' ? getChoiceA : getChoiceB;
      }
    );

    expect(selector(state)).toBe('aaa');
    expect(selector(state)).toBe('aaa');
    expect(selector.recomputations()).toBe(1);

    state = { ...state, choice: 'choiceB' };
    expect(selector(state)).toBe('bbb');
    expect(selector(state)).toBe('bbb');
    expect(selector.recomputations()).toBe(2);

    state = { ...state, choiceB: 'BBB' };
    expect(selector(state)).toBe('BBB');
    expect(selector.recomputations()).toBe(2);
  });
});