perf. Quizz Solution : const makeGetVeryComplexeStuff = () => createSelector((state, { id }) => computeSomeStuffs(state, id)) const makeMapStateToProps = () => (state, props) => { const getVeryComplexeStuff = makeGetVeryComplexeStuff(); return { complexStuff: getVeryComplexeStuff(state, props), } } Oui ! const getVeryComplexeStuff(state, props) = createSelector( (state, { id }) => computeSomeStuffs(state, id) ) const mapStateToProps = (state, props) => ({ complexStuff: getVeryComplexeStuff(state, props), });