JavaScript is a popular programming language known for its asynchronous nature. When dealing with asynchronous operations, it is common to use Promises to handle callbacks and ensure a more structured approach to managing asynchronous code.

One handy method available for Promises in JavaScript is the finally() method. In this blog post, we will explore what the finally() method does and how to use it effectively.

Table of Contents

• What is Promise.finally()?
• Usage
• Example
• Benefits of using finally()
• Conclusion

What is Promise.finally()?

The finally() method is a part of the Promise API that allows you to register a callback function that will be invoked regardless of whether the Promise is resolved or rejected. It provides a way to perform clean-up tasks or execute code that needs to be run at the end of a Promise chain, irrespective of its outcome.

Usage

The finally() method can be used by chaining it onto a Promise. Syntaxically, it is placed after the then() or catch() methods and before the closing semicolon.

Here’s its syntax:

promise
  .then(onFulfilled)
  .catch(onRejected)
  .finally(onFinally);

The onFinally callback will be executed whether the Promise is resolved or rejected.

Example

Let’s consider an example where we fetch data from an API using Promises. We want to display a loading spinner while the data is being fetched, regardless of whether the request succeeds or fails.

function fetchData() {
  showSpinner();

  return fetch('https://api.example.com/data')
    .then(response => response.json())
    .then(data => {
      // Handle the data
      showData(data);
    })
    .catch(error => {
      // Handle the error
      showError(error);
    })
    .finally(() => {
      hideSpinner();
    });
}

fetchData();

In the above example, the finally() method is used to hide the loading spinner, ensuring that the spinner is always removed, no matter the outcome of the Promise.

Benefits of using finally()

The finally() method has several benefits when working with Promises:

• It allows you to consolidate code that needs to be executed regardless of the Promise outcome.
• It avoids code repetition by providing a single place to handle clean-up tasks.
• It gives you a way to handle final operations, such as hiding loaders, closing connections, and releasing resources.

Conclusion

The finally() method in JavaScript is a powerful tool that allows you to execute code at the end of a Promise chain, whether the Promise is resolved or rejected. This makes it a valuable addition to your asynchronous programming toolkit. By using finally(), you can easily handle clean-up tasks and ensure consistent behavior in your applications.

Remember to take advantage of the finally() method in your asynchronous JavaScript code to improve the readability and maintainability of your projects.

#javascript #asynchronous