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How to type an async Function in TypeScript?

How to type an async Function in TypeScript?

How to type an async Function in TypeScript?

How to type an async Function in TypeScript?

TypeScript is a typed superset of JavaScript that adds optional static type checking to the language. This means that TypeScript can help you catch errors in your code before you even run it. One of the benefits of using TypeScript is that it can help you type your asynchronous functions. This can make your code more readable and maintainable.

What is an async function?

An async function is a function that can perform asynchronous operations. This means that the function can run without blocking the main thread of execution. Asynchronous functions are useful for performing operations such as fetching data from a remote server or uploading a file to a cloud storage service.

How to type an async function in TypeScript

To type an async function in TypeScript, you need to specify the return type of the function. The return type of an async function is always a Promise. This means that the function will return a Promise object that represents the eventual result of the operation.

For example, the following async function fetches a user from a remote server and returns a Promise object that resolves to the user object:

async function getUser(id: number): Promise<User> {
  const response = await fetch(`/api/users/${id}`);
  const user = await response.json();
  return user;
}

The return type of the getUser() function is Promise<User>. This means that the function will return a Promise object that resolves to a User object.

Using async functions in TypeScript

Once you have typed your async functions, you can use them in your TypeScript code like any other function. However, it is important to remember that async functions always return a Promise. This means that you need to use the await keyword to wait for the Promise to resolve before you can use the result.

For example, the following code fetches a user from the remote server and then prints the user's name to the console:

const user = await getUser(1);
console.log(user.name);

The await keyword tells TypeScript to wait for the getUser() function to return before printing the user's name to the console.