Multiparameter Memoization: Example

tieredMemoize.example.js

const reselect = require('reselect');
const createSelectorCreator = passSelectorCountToMemoizer(reselect.createSelectorCreator);
const createSelector = createSelectorCreator(createTieredMemoizer({ memoizers: [multiMemo] }));

const getFooBy = (state, id) => state.foos.byId[id];
const getBar = state => state.bar;
const getBaz = state => state.baz;

const getStuff = createSelector(
  getFooBy, getBar, getBaz,
  // something something createStructuredSelector.
  (foo, bar, baz) => ({ foo, bar, baz })
);

const state0 = {
  foos: {
    byId: {
      '1': { name: 'Foo' },
      '2': { name: 'Fooby' },
      '3': { name: 'Fooborp' },
    },
  },
  bar: 'Bar!',
  baz: 'Baz!',
};

const state1 = {
  ...state0,
  foos: {
    byId: {
      ...state0.foos.byId,
      '2': { name: 'Foobifoob' },
    },
  },
};

const a00 = getStuff(state0, '1');
const a01 = getStuff(state0, '1');
const a10 = getStuff(state1, '1');
const a02 = getStuff(state0, '2');
const a11 = getStuff(state1, '1');

console.log(`getStuff(id = '1'):`, JSON.stringify(a00));
console.log(`  Does it return the same value for the same state?`, a00 === a01);
console.log(`  Does it return the same value when something else in the state is different?`, a01 === a10);
console.log(`  Does it return the same value between other selections?`, a10 === a11);