Typing Async Code

An async function always returns a Promise, and TypeScript tracks what it resolves to: async function load(): Promise<Star[]>. await unwraps it, so the awaited value has the inner type. Promise.all keeps each position's type in a tuple, and Awaited<T> does the unwrapping at the type level. Give data-loading functions an explicit return type so every caller is checked against it.

How it reads

• Promise<Star[]> is checked against every return inside the function
• await turns Promise<Star[]> into Star[]
• Promise.all gives a tuple: [Star[], number]

Cloud tip: An async function can never return a plain value to its caller. Remember to await it, or the caller gets a Promise.