06 — Functions & Overloads

Core Concepts

• Parameter types — must always be annotated
• Return types — inferred, but annotate public APIs
• Optional parameters — param?: Type (always at the end)
• Default parameters — param: Type = defaultValue
• Rest parameters — ...args: Type[]
• Function overloads — multiple signatures, one implementation
• this parameter — explicit this typing in function signatures
• Callable types — type Fn = (x: number) => string
• void vs undefined — void callbacks allow returning values; undefined doesn't

Overloads vs Union Returns