Difference Between Promise and Async Await in Node.js

The Different Ways to Handle the Asynchronous Code in NodeJS

Before diving into Promises and Async/Await, it's essential to understand the traditional method of handling asynchronous code in Node.js: callbacks.

Callbacks

Callbacks have been a fundamental part of Node.js since its inception. They allow you to specify a function that should be executed when an asynchronous operation completes. While callbacks are functional, they can lead to callback hell or a pyramid of doom when dealing with multiple nested asynchronous operations.

Promises

Promises in Node.js are a way to deal with tasks that take some time to finish, like reading a file or making a network request. Think of a Promise as a special container for a task that can be in one of three states:

• Pending : The task is still ongoing.
• Resolved: The task has finished successfully, and you get the result you wanted.
• Rejected: The task encountered a problem or an error occurred.

Error Handling of Promises

Promises come with built-in error-handling mechanisms. You can attach a .catch() method to a Promise to handle errors that occur during its execution. This makes error handling more elegant and centralized compared to callbacks.

Example: Here's an extended example that demonstrates error handling using .catch() with Promises in Node.js

Async/Await

Async/Await is a more recent addition to JavaScript, further simplifying asynchronous code. It is built on top of Promises and provides a more synchronous-looking syntax for handling asynchronous operations. You can mark a function as async to use the await keyword inside it, which waits for a Promise to resolve before continuing execution.

Error Handling in Async/Await

Error handling in Async/Await is an essential aspect of writing robust and reliable asynchronous code in Node.js and JavaScript in general. Async/Await provides a more straightforward and synchronous-looking way to handle errors compared to traditional callback-based approaches. Here's how error handling works in Async/Await:

Use of Try-Catch Blocks :

Async/Await leverages traditional try-catch blocks to handle errors. When you mark a function as async and use the await keyword within it to await a Promise, any errors that occur during the execution of that Promise can be caught using a try-catch block.

Throwing Errors:

Inside an async function, if you encounter an issue or want to propagate an error, you can use the throw statement. This will cause the function to exit and the error to be caught by the nearest try-catch block or handled by the caller of the async function.

Handling Multiple Promises with Async/Await:

When dealing with multiple Promises concurrently, you can use Promise.all() along with Async/Await to handle errors collectively. If any of the Promises within Promise.all() reject, it will trigger the catch block.

Best Practices for Using Promises and Async/Await:

• Choose the Right Tool
• Use Async/Await for Readability
• Promisify Where Needed
• Handle Errors Gracefully
• Use Promise.all() for Concurrent Operations
• Avoid Callback Hell
• Keep Functions Small and Focused
• Promote Consistency

When choosing between Promises and Async/Await in Node.js, it's essential to consider:

• Simplicity vs. Speed: Async/Await is often favored for its simplicity and readability. However, it may introduce slight overhead compared to Promises because of the additional work required by the JavaScript runtime to manage async and await operations.
• Micro-Optimizations: In some rare cases, if you need to fine-tune performance, you might choose Promises over Async/Await for specific operations.
• Concurrency and Parallelism: If you need to execute multiple asynchronous operations concurrently, both Promises and Async/Await can be used effectively. However, you must be cautious with large-scale concurrency, as it can lead to resource contention and performance bottlenecks.
• Error Handling Overhead: Async/Await's error handling using try-catch blocks is generally more straightforward and can lead to better code optimization by the JavaScript engine. In contrast, Promises' error handling with .catch() might introduce a slightly higher cost in terms of performance, though it's usually insignificant.
• Promisify Overhead: When converting callback-based APIs to Promises using utilities like util. promisify, there is a slight performance overhead involved in creating these Promises.

Difference Between Promise and Async/Await

These differences highlight the advantages of Async/Await for developers in terms of code readability and error handling, while Promises continue to be essential for maintaining and working with existing codebases. The choice between them ultimately depends on your project's requirements, coding style, and the need for backward compatibility.