Conditional Types Development Tutorials, Guides & Insights

type IsString<T> = T extends string ? 'Yes' : 'No';

type A = IsString<string>; // 'Yes'
type B = IsString<number>; // 'No'

This type checks whether a given type is a string and returns 'Yes' or 'No' accordingly.

TypeScript’s type inference allows the compiler to determine types automatically without explicit annotations.

let name = 'Alice'; // inferred as string
let age = 30;       // inferred as number
let isDeveloper = true; // inferred as boolean