TypeScript in Depth · Typing React · Lesson 12 of 16
Typing useState
Concept
Typing useState
useState infers its type from the initial value, but you can specify it explicitly for cases like starting with null.
By the end of this lesson
- Explain the core idea behind Typing useState.
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in Typing useState. Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Type a useState hook that holds an array of numbers, starting empty.
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