Async and Await in Node.js

Level : Advanced
Mentor: Shailendra Chauhan
Duration : 00:04:00

What is the Async Function?

Async functions in Node.js, denoted by the async keyword, make asynchronous code easier to read and maintain. These functions support the await keyword, which enables the sequential and synchronous execution of asynchronous operations. 

What is Await?

Await is a keyword used with async functions that tell the JavaScript interpreter to pause until the next asynchronous operation is performed. You can also store the value in a variable to use later. It is vital to remember that the keyword await can only be used in the bodies of async functions.

Why do we use async/await?

  • Async/await enables Node.js to perform asynchronous actions without interrupting the event loop.
  • It simplifies asynchronous code, making it appear more synchronous and understandable.
  • When compared to typical callback-based alternatives, this method provides a more systematic approach to error handling.
  • Allows you to write asynchronous code sequentially, which improves code organization and maintainability.
  • Async/await can improve efficiency by minimizing callback layering and streamlining code execution.

How does Async/Await Work?

  • The "async" keyword specifies that a function is asynchronous.
  • This notifies JavaScript that the function will run asynchronously and should return a Promise.
  • Within an asynchronous function, you can use the "await" keyword to suspend execution until a Promise is resolved.
  • This causes the code to look and behave like synchronous code, even though it is asynchronous.
  • When a Promise is resolved, the "await" keyword returns the resolved value.
  • This value can then be utilized in the next line of code.
  • If the Promise is refused, an error is thrown, which can be caught using a try/catch block.

Declare an Async Function

The async keyword can be used to declare a function easily. All async functions generate promises, which automatically encapsulate non-promise values. To make a function async, use the keyword async before its declaration.

Advantages of Async and Await 

  • Error Handling: Improves and simplifies error handling in asynchronous programs.
  • Supports Conditional Statements: Allows you to use conditional logic in asynchronous functions.
  • Intermediate Values: Enables the capture and use of intermediate values in asynchronous activities.
  • Debugging: Helps to debug asynchronous programming by providing a clear execution path.
  • Synchronous & Asynchronous Expressions: Allows you to await both asynchronous and synchronous expressions, which improves code readability and organization.

Use Async/Await with Promises

Async/Await is based on Promises and can be used in combination with them to make asynchronous programming easier to deal with. 

What are promises?

Promises enable an asynchronous action to run and wait for the value while also executing any subsequent code (known as "callbacks") in the meantime. Callbacks were initially invoked by giving them as arguments.

Debugging Async/Await

Here are some pointers for you to debug async/await code.

  • Use a debugger: Most programming languages provide built-in debuggers that allow you to step through your code line by line and check the values of variables. Use the debugger to figure out where your code is getting stuck or where data isn't being returned as planned.
  • Check for errors: Async/await code is susceptible to defects like race situations, deadlocks, and timing concerns. Make certain to check for mistakes by including an error-handling function and logging error messages.
  • Use logging: Logging might be useful for debugging async/wait code. Logging is useful for recording variable values, tracking the flow of your code, and debugging any errors that develop.
  • Test for concurrency issues: Async/await code frequently contains numerous concurrent operations. Check for concurrent difficulties, such as race situations and deadlocks, and utilize synchronization techniques like locks and semaphores to avoid them.
  • Break down complex operations: If your async/await code involves complex processes, consider breaking them down into smaller, more manageable chunks. This might help you discover and debug any difficulties that develop.

Managing Errors using Async/Await

Rejected promises might result in unhandled promise errors if error handling isn't implemented, which could lead to unpredictable behavior from your application. Async functions can employ try/catch blocks, which allow you to try several actions within a block and then catch any issues that arise during execution, which are handled in the catch block.

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