Conditional Types

Conditional types work like type-level if/else. ## Syntax ```ts T extends U ? X : Y ``` ## Example ```ts type IsString<T> = T extends string ? true : false; type A = IsString<string>; // true type B = IsString<number>; // false ``` ## Practical example ```ts type ApiResult<T> = T extends Error ? { ok: false } : { ok: true; data: T }; ``` ## Graph ```mermaid flowchart TD A[T] --> B{extends?} B -->|Yes| C[Type X] B -->|No| D[Type Y] ``` ## Remember - Conditional types adapt APIs - Powerful for libraries