Basic Selectors

Basic Selectors Overview

Basic Selectors is something you will reach for often in Redux. It keeps your workflow predictable and makes your intent obvious to reviewers and teammates.

When you learn basic selectors properly, you avoid the guesswork that leads to mistakes and rework. The example below shows the shape you will use in most real Redux projects.

import { createSelector } from '@reduxjs/toolkit';

const selectItems = (state) => state.cart.items;

export const selectCartTotal = createSelector(
  [selectItems],
  (items) => items.reduce((sum, i) => sum + i.price * i.qty, 0),
);

createSelector memoizes derived data so it only recomputes when its inputs change.

Basic Selectors Example

const slice = createSlice({ name, initialState, reducers });
const store = configureStore({ reducer: { key: slice.reducer } });
// dispatch(slice.actions.something())

• Start from a minimal Basic Selectors example and grow it only as needed.
• Keep things explicit so Basic Selectors behaves the same for everyone on the team.
• Name things clearly so teammates understand your Basic Selectors at a glance.
• Verify Basic Selectors works as expected before relying on it in important work.

Redux Cheatsheet

Quick Redux Toolkit reference related to basic selectors.

How Basic Selectors Works in Redux

Basic Selectors follows Redux's predictable data flow: components dispatch actions, reducers compute the next state from the previous state and the action, and subscribed components re-render.

createSelector memoizes derived data so it only recomputes when its inputs change.

• State lives in a single, read-only store.
• Actions are the only way to describe a change.
• Reducers are pure functions that return the next state.
• Redux Toolkit removes most boilerplate with slices and thunks.

Practical Guidance for Basic Selectors

In modern apps, basic selectors should use Redux Toolkit rather than hand-written Redux. Keep state minimal, colocate logic in slices, and use RTK Query for server data.

Common Mistakes

• Skipping edge cases and error handling when using basic selectors.
• Not verifying the result of basic selectors before moving on.
• Over-complicating basic selectors before you actually need the extra flexibility.
• Ignoring documentation, which makes basic selectors hard for the next person to follow.

Key Takeaways

• Basic Selectors is a core part of working effectively with Redux.
• Start small and keep basic selectors focused on a single goal.
• Apply consistent patterns so basic selectors scales across your project.
• Practise and document basic selectors to keep your workflow maintainable.