Why Async Functions in TypeScript Always Return a Promise

📌Intro

You write a simple asyncfunction, return 42, and suddenly TypeScript yells:
“Type 'number' is not assignable to type 'Promise'.”
Why can’t an async function just return a value? Let’s break it down.

🧠Context & Why:

The asynckeyword in TypeScript (and JavaScript) changes how the function behaves:

• Every asyncfunction always returns aPromise<T>.
• Even if you return a raw value, it’s wrapped in Promise.resolve(value).

Examples:

// Normal function function getFavoriteNumber(): number { return 26; } // Async function async function getFavoriteNumber(): Promise<number> { return 26; // Actually Promise.resolve(26) } // Arrow version const getFavoriteNumber = async (): Promise<number> => { return 26; }; 

If you try:

async function getFavoriteNumber(): number { return 26; } 

TypeScript error:

Type 'number' is not assignable to type 'Promise<number>'. 

Real-Life Example:

You might start with a hardcoded value, but later fetch it from an API. Making it async upfront saves refactoring:

const getFavoriteNumber = async (): Promise<number> => { const res = await fetch("/api/fav-number"); const data = await res.json(); return data.number; }; 

💡Think of asyncas a “Promise factory.” Whatever you return gets gift-wrapped in a Promise.