useReducer

What this means

useReducer is another way to manage state. Instead of calling many setters, you dispatch actions to a reducer function that returns the next state.

In beginner terms, this topic answers one practical question: "What should I write, and why does React care about it?" Do not try to memorize the syntax first. First understand the idea, then connect the syntax to that idea.

Why it matters

Reducers are useful when state has several related transitions, such as a form builder, cart, quiz flow, or editor.

When you build real React screens, this idea helps you decide where data should live, what the user should see, and what should happen after an interaction. That is why this lesson is part of the main path instead of being an optional detail.

Step by step

1. Notice the UI problem this topic solves. 2. Look at the smallest possible example. 3. Change one value and predict what should appear. 4. Run the example and compare the result with your prediction. 5. Use the practice task before moving on.

Small example

function reducer(state, action) {
  if (action.type === "increment") return { count: state.count + 1 };
  return state;
}

Common mistake

Do not use reducers for every tiny state value. useState is simpler for one or two independent values.

Practice task

Create a reducer with increment and reset actions for a counter.

Remember this

Reducers make state transitions explicit.