Type what goes into a function, what comes out, and let TypeScript catch mistakes for you.
TypeScript lets you describe both the parameters a function accepts and the value it returns. This helps catch mistakes such as passing the wrong type of value or using an unexpected return value.
Function types become more powerful when working with optional parameters, default values, rest parameters, callbacks, and overloaded functions. These features help you create reusable functions with clearly defined behavior.
What you'll walk away knowing