TypeScript with React
Typing Custom Hooks
Type return values, tuple returns with as const, and generic custom hooks.
Last Updated: July 29, 2026
•
10 min read
Custom React hooks encapsulate state logic and return typed objects or tuple pairs ([value, setValue] as const).
1. Introduction & Architecture
2. Deep Dive & Core Concepts
When returning arrays from custom hooks, append as const to infer fixed tuple element types instead of union arrays.
3. Basic Code Example
4. Advanced Production Patterns
5. Interactive Code Playground
console.log("Custom hooks typed with tuple and generic returns.");6. Common Pitfalls & Edge Cases
Warning: Forgetting
as const on array return tuples causes TS to infer (boolean | (() => void))[] array unions!7. Interview Q&A & Quizzes
Q: Why use 'as const' when returning tuples from custom hooks?
A: It prevents TypeScript from widening the return type into an array union, preserving exact tuple positions.
8. Summary Comparison Table
| Return Pattern | Without as const | With as const |
|---|
[state, setter] | (State | Setter)[] | readonly [State, Setter] |