Custom hooks

What this means

A custom hook is a function whose name starts with use and can call other hooks. It lets you reuse stateful logic without copying component code.

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

Custom hooks keep components focused. If several components need the same behavior, a hook can hold that behavior in one place.

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 useToggle(initial = false) {
  const [value, setValue] = React.useState(initial);
  return [value, () => setValue((current) => !current)];
}

Common mistake

Do not call hooks conditionally inside custom hooks. The same rules of hooks still apply.

Practice task

Create a useCounter hook that returns count, increment, and reset.

Remember this

Custom hooks share behavior, not UI.