TypeScript Null and Undefined

In JavaScript, many bugs happen because values are missing. TypeScript helps you **handle missing values safely**. ## What are null and undefined? - undefined: value not assigned - null: intentionally empty ```ts let a: number; console.log(a); // undefined let b: number | null = null; ``` ## The problem in JavaScript ```ts let name = null; console.log(name.length); // crash at runtime ``` ## TypeScript safety ```ts let name: string | null = null; // name.length ❌ error if (name) { console.log(name.length); // safe } ``` ## strictNullChecks When enabled: - null/undefined must be handled explicitly - prevents runtime crashes ## Optional chaining ```ts type User = { profile?: { email: string } }; const user: User = {}; console.log(user.profile?.email); // undefined, safe ``` ## Graph ```mermaid flowchart LR A[Value] --> B{null/undefined?} B -->|Yes| C[Handle safely] B -->|No| D[Use value] ``` ## Remember - Always handle null/undefined - Use strictNullChecks - Optional chaining avoids crashes