Type Guard

Definitions

1. A runtime check that narrows the type of a variable within a conditional block. In TypeScript, type guards use typeof, instanceof, or custom predicates to tell the compiler a value is a more specific type.

   In plain English: A check in your code that proves to both you and the compiler that a value is a specific type, unlocking access to that type's properties.

   Example: "Add a type guard so TypeScript knows the response is a User, not just unknown."

Related Terms

• Declaration File
• Discriminated Union
• Generics
• Type Hints
• Union Type
• Utility Types
• Structural Typing
• Partial Type
• Type Predicate
• Zod