20 Async/Await Interview Questions and Answers

Async/Await is a relatively new addition to the JavaScript language that allows developers to write asynchronous code in a more synchronous fashion. When applying for a position that involves JavaScript, it is likely that you will be asked questions about Async/Await. In this article, we discuss the most commonly asked Async/Await questions and how you should respond.

Async/Await Interview Questions and Answers

Here are 20 commonly asked Async/Await interview questions and answers to prepare you for your interview:

1. Can you explain what asynchronous programming is?

Asynchronous programming is a form of programming that allows for tasks to be completed out of order. This means that a program can start a task and then move on to other tasks before the first one is completed. This can be helpful in situations where a task might take a long time to complete, but the program doesn’t need to wait for it to finish before moving on.

2. How does async/await help with performance and scalability?

Async/await can help improve performance and scalability by allowing your application to do other work while it is waiting for a task to complete. This can help avoid bottlenecks and keep your application responsive. Additionally, using async/await can help reduce the overall amount of code needed to be written, making your application easier to maintain.

3. Can you explain the difference between an async function and a regular function in JavaScript?

Async functions are functions that allow you to use the await keyword to wait for a promise to resolve before continuing execution of the function. Regular functions do not have this ability, and will instead execute the code inside of them immediately.

4. What are some of the advantages of using async functions in JavaScript?

Async functions help to make code simpler and easier to read. They also can make code execution more efficient by allowing tasks to be run in parallel.

5. What do you understand about await in JavaScript?

The await keyword in JavaScript is used to pause the execution of a function until a Promise is resolved. This allows you to write asynchronous code that looks and feels like synchronous code.

6. Is it possible to use async/await with promise chains? If yes, how can this be achieved?

Yes, it is possible to use async/await with promise chains. In order to do this, you must first await the initial promise in the chain, and then you can continue working with the results of that promise as if they were synchronous. This can be a useful way to avoid callback hell when working with asynchronous code.

7. What’s the error handling strategy for promises that were rejected while awaiting?

There are a couple different ways to handle errors with async/await. The first is to use a try/catch block around your code. The second is to add a .catch() handler to your promise.

8. In which scenarios would you use synchronous code instead of asynchronous code?

There are a few reasons you might choose to use synchronous code instead of asynchronous code. One reason is if you are working with a very small amount of data that can be processed quickly. Another reason is if your code is already running in a synchronous environment and you don’t want to introduce the overhead of using asynchronous code. Finally, you might also choose to use synchronous code if you need to guarantee that certain operations will happen in a specific order.

9. Can you give me some examples of real world applications where async/await has been used?

Async/await has been used in a variety of real world applications, including:

-Web applications that need to load data from multiple sources simultaneously
-Chat applications that need to send and receive messages in real-time
-Games that need to perform complex calculations in the background while still providing a responsive experience to the user

10. Why are callback functions called after a certain amount of time even though the actual work was completed before the specified time interval?

This is due to the way that async/await functions work. When an async function is called, it will return immediately, even if the actual work is not yet finished. This is why callback functions are often used with async functions, so that the callback can be called when the work is actually finished.

11. Are callbacks executed on their own thread or the main execution thread?

Callbacks are executed on the main execution thread.

12. How is concurrency managed when using async/await?

When using async/await, concurrency is managed by the async keyword. When an async function is called, the code inside of the function is executed asynchronously. This means that the code will not block the main thread, and other code can continue to execute while the async function is running.

13. What is the best way to avoid deadlocks when using async/await?

One of the best ways to avoid deadlocks when using async/await is to avoid using the await keyword inside of a lock statement. If you need to use await inside of a lock statement, then you should use a SemaphoreSlim object instead of a regular lock object.

14. How does asynchronicity affect the CPU during runtime?

Async/await is a way of handling asynchronous tasks in a synchronous manner. This means that the CPU will not be blocked while waiting for an asynchronous task to complete. This can help improve performance by allowing the CPU to continue working on other tasks while the asynchronous task is being handled.

15. What are the different ways that async/await can be implemented in JavaScript?

There are three different ways that async/await can be implemented in JavaScript:

1. Using the async keyword: This keyword can be used to declare a function as asynchronous.

2. Using the await keyword: This keyword can be used inside of an async function in order to pause the execution of the function until a Promise is resolved.

3. Using Promises: Promises can be used in conjunction with async/await to handle asynchronous operations.

16. What is the purpose of the Promise constructor in JavaScript?

The Promise constructor is used to create a new Promise object. A Promise object represents an asynchronous operation, and can be used to track the status of that operation. A Promise can be in one of three states: pending, fulfilled, or rejected.

17. Tell me something about the ‘async’ keyword in ECMAScript 2017.

The ‘async’ keyword is used to denote that a function is asynchronous. This means that the function will not block the main thread, and will instead run in the background. This can be useful for tasks that are not time-sensitive, or that may take a long time to complete.

18. Is it possible to nest async functions in JavaScript? If yes, then how?

Yes, it is possible to nest async functions in JavaScript. You would do this by simply declaring an async function within another async function. The inner function will then execute asynchronously with respect to the outer function.

19. Can you explain how async/await differs from generators?

Async/await is a newer way to handle asynchronous code in JavaScript, while generators are a older way to do so. Async/await is generally seen as being easier to use and understand, while generators can be more powerful.

20. What do you understand about microtasks vs macrotasks?

Microtasks are tasks that are executed after the current task has finished. They are typically used for cleanup tasks or for tasks that need to be executed on the next event loop. Macrotasks are tasks that are executed on the current event loop. They are typically used for longer-running tasks that need to be executed immediately.