What does ‘async’ in a function declaration do in a function without ‘await’?

When working with TypeScript, you may come across the ‘async’ keyword in function declarations. This keyword is used to define an asynchronous function, which means that the function will return a Promise. However, if the function does not contain any ‘await’ expressions, you might wonder what the purpose of using ‘async’ is. In this article, we will explore the implications of using ‘async’ in a function without ‘await’ and discuss possible use cases.

Understanding the ‘async’ Keyword

The ‘async’ keyword is a syntactic sugar introduced in ECMAScript 2017 (ES8) to simplify working with Promises. When you declare a function as ‘async’, it automatically wraps the return value in a Promise. This allows you to use the ‘await’ keyword within the function to handle asynchronous operations in a more readable and synchronous-like manner.

Using ‘async’ Without ‘await’

Although it is common to use ‘async’ and ‘await’ together, it is not mandatory. You can still use the ‘async’ keyword in a function without any ‘await’ expressions. In this case, the function will behave like a regular function, but with the added benefit of returning a Promise.

One possible use case for using ‘async’ without ‘await’ is when you want to create a function that performs some asynchronous setup or initialization, but you don’t need to wait for the result. For example, you might want to fetch some data from an API and store it in a global variable for later use:

async function fetchData() {
  const response = await fetch('https://api.example.com/data');
  const data = await response.json();
  // Store the data in a global variable
  window.myData = data;
}

In this example, the ‘fetchData’ function fetches data from an API and stores it in the ‘myData’ global variable. The function is declared as ‘async’ because it uses the ‘await’ keyword to handle the asynchronous fetch operation. However, since there is no need to wait for the result of this function, it can be called without using ‘await’:

// Call the function without 'await'
fetchData();
console.log('Data fetching started...');

By calling the ‘fetchData’ function without ‘await’, the data fetching process starts asynchronously, and the execution continues to the next line immediately. This can be useful when you want to initiate an asynchronous operation without blocking the main thread.

Conclusion

In TypeScript, the ‘async’ keyword in a function declaration indicates that the function returns a Promise. Even if the function does not contain any ‘await’ expressions, it can still be useful in certain scenarios where you want to perform asynchronous setup or initialization without waiting for the result. By understanding the implications of using ‘async’ without ‘await’, you can leverage this feature to write more flexible and efficient code.