LESSON 2.2
Constraints and default type parameters
Learn key techniques and workflows in TypeScript for Application Developers.
4m
intermediate
17,541 students
Overview
Constraints say what a type parameter must at least be. Combined with keyof, they give you property access that stays typed.
In this lesson you will:
- Constrain a parameter with extends
- Use keyof to type property access generically
- Give a type parameter a sensible default
Pro Tip
Use caching and revalidation wisely to ensure your app stays fast and data remains fresh without unnecessary requests.