As you already know JavaScript is a single-threaded language and it can perform one action at a time. However, many operations in web development including pulling data from a server or reading the files in the disk can take some time to be accomplished. If it does perform these operations synchronously, meaning JavaScript has to wait until the operation is done before going to the next line of code, then it will slow down the responsiveness of the application. To complete such tasks more efficiently, JavaScript employment asynchronous programming technique.

What Are Asynchronous Operations?

Asynchronous operations are operations which are initiated at the current time but allowed to finish at some other time while the program continues with other lines of code. In JavaScript the handling of asynchronous behavior is done through the use of callbacks, promises, and latterly the async/await syntax. This approach makes the JavaScript perform tasks in the background thereby enhancing the overall performance of web apps.
For instance, consider the case in a web application where information about a user has to be retrieved from the database. This process could take a few seconds depending on the speed of the network or high traffic to the server. JavaScript can continue with the rest of the code instead of halting the application as it waits for the data to be received. This kind of non-blocking behavior is the basic idea behind asynchronous programming.

Introducing async/await

The async/await syntax, which is a part of ES2017 (ES8), is arguably the most elegant and easy-to-understand means to deal with asynchronous code. It is based on Promises and gives a way to look asynchronous code like synchronous code for easy to understand and maintain.
An async function is a function that has the Promise as its return type. The async keyword when attached to a function tells the program that the function will always return a Promise regardless of whether a Promise is actually being returned or not. Await is used inside an async function to allow the function to wait for a promise to complete or reject.

How Does async/await Work?

Now let me illustrate with an example how use async/await. Consider the following code snippet that retrieves a user’s shopping cart and displays it:

In this example, the getCart function is declared as async, therefore, it can use the await keyword for handling asynchronous operations within it.

1. const cart = await req.user.getCart();: This calls the getCart method on the user object, this retrieve the current cart instance of the user. The await keyword ensures that JavaScript wait for the Promise returned by getCart() to be completed. The resolved value (the user’s cart) is then assigned to the cart variable.
2. const products = await cart.getProducts();: Likewise, this line pauses the execution of the code until the getProducts method is done, which brings the products in the user’s cart. The await keyword tells the CLR that the following line of code should not execute until the product data is ready.
3. Rendering the Response: Upon completion of both asynchronous operations, the variable res.render() is executed to render the cart page alongside the products.
4. Error Handling with try...catch: The try...Finally, catch block is employed to handle any exceptions that may arise due to the asynchronous operations. If there is an error at any of the await statements, the catch block handles the error and logs it to the console.

Benefits of using async/await

The async/await syntax offers several advantages over traditional promise-based code:The async/await syntax offers several advantages over traditional promise-based code:
• Improved Readability: It is easy to follow and comprehend because the code looks like normal synchronous code despite its ability to handle asynchronous operations.
• Error Handling: Using try...Async/await makes error handling as simple and uniform as catching the error with sync/async.
• Simplifies Complex Operations: async/await should be used for the code which has multiple asynchronous operations because the code would be easier to be written, tested, and debugged.

Conclusion

Async programming is particularly crucial in JavaScript to execute computationally intensive operations without stalling the main thread. The async/await syntax offers some more sophisticated way of dealing with these operations and the code generated is more readable, cleaner and easier to debug. Async/await helps developers to write asynchronous code, which makes their application more predictable and faster.