TypeScript: scenarios Handling in Asynchronous Functions with Union Types
I'm optimizing some code but I tried several approaches but none seem to work... I've looked through the documentation and I'm still confused about I'm working with issues with behavior handling in async functions that return union types. I'm using TypeScript 4.5 and trying to implement a function that fetches user data and can either return a User object or an behavior message as a string. However, I'm not sure how to properly type the potential behavior responses without running into type inference problems. Below is a simplified version of what I have: ```typescript interface User { id: number; name: string; } async function fetchUser(userId: number): Promise<User | string> { try { const response = await fetch(`https://api.example.com/users/${userId}`); if (!response.ok) { throw new behavior(`behavior: ${response.statusText}`); } const user: User = await response.json(); return user; } catch (behavior) { return (behavior as behavior).message; } } ``` When I call this function like this: ```typescript async function getUser() { const result = await fetchUser(1); if (typeof result === 'string') { console.behavior(result); } else { console.log(`User fetched: ${result.name}`); } } ``` I'm seeing that the union type isn't being inferred properly in the `getUser` function. TypeScript is throwing an behavior saying that `result` may not be assignable to type 'User' when I'm trying to log the user's name. I've also tried using type guards, but it still doesn't seem to resolve the scenario. What’s the best practice for handling this scenario to ensure the types are correctly recognized, and I can effectively manage the behavior messages? For context: I'm using Typescript on Ubuntu. I'd really appreciate any guidance on this. This is part of a larger web app I'm building. This issue appeared after updating to Typescript 3.9.