reselect test

hoge.js

const { createSelector } = require('reselect');

const ids = [1,2,3];

const byIds = {
  1: {
    name: 'one'
  },
  2: {
    name: 'two'
  },
  3: {
    name: 'three'
  }
};

const selector = createSelector(
  (state) => state.ids,
  (state) => state.byIds,
  (ids, byIds) => ids.map(id => byIds[id])
);

const state1 = { ids, byIds };
const items = selector(state1);
const state2 = {
  ids,
  byIds: {
    ...byIds,
    '3': {
      name: 'THREE'
    }
  }
};
console.log(items === selector(state1)); // true
console.log(items === selector(state2)); // false
console.log(items === selector(state1)); // false, cache expired
console.log(selector(state2)); // [ { name: 'one' }, { name: 'two' }, { name: 'THREE' } ]