TYPES-type-guards

What problem does it solve?

Handling dynamic data and union types in TypeScript often requires runtime checks, but without proper type guards, type safety is lost, leading to potential runtime errors. This Skill enables safe type narrowing.

Core Features & Use Cases

• Built-in Guards: Learn to use typeof, instanceof, in, and Array.isArray() for basic type narrowing.
• Custom Type Predicates: Write reusable functions that return value is Type to safely narrow object shapes and complex logic.
• Discriminated Unions: Leverage literal type properties to easily narrow down union types.
• Assertion Functions: Implement functions that throw an error if a type check fails, asserting the type for the remainder of the scope.
• Use Case: Implement a type guard isProduct to safely narrow an unknown value to a Product interface, then use it to process a list of mixed data, ensuring type safety and preventing runtime crashes.

Quick Start

Create a type predicate isStringArray that checks if an unknown value is an array of strings, then use it to process a dynamic input.