Async-Await and Promises in Node JS

Promises and async/await are two mechanisms in JavaScript that allow developers to handle asynchronous operations in a more readable and maintainable way.

Promises

Promises are a built-in JavaScript object that represent an asynchronous operation that may or may not have completed yet. A promise can be in one of three states: pending, fulfilled, or rejected. Promises are used to handle values that may not be available yet, such as the result of an asynchronous operation.

Here is an example of how to use a promise in a Node.js application:

const fs = require('fs').promises

fs.readFile('file.txt')
  .then(data => console.log(data))
  .catch(err => console.error(err))

In this example, the fs.readFile() function returns a promise that represents an asynchronous operation. The then() method is used to handle the fulfilled state of the promise, which means that the operation completed successfully. The catch() method is used to handle the rejected state of the promise, which means that an error occurred during the operation.

Async/Await

Async/await is a more recent addition to JavaScript that allows developers to write asynchronous code in a synchronous style. Async/await builds on top of promises and provides a cleaner and more readable syntax for handling asynchronous operations.

Here is an example of how to use async/await in a Node.js application:

const fs = require('fs').promises

async function readFile() {
  try {
    const data = await fs.readFile('file.txt')
    console.log(data)
  } catch (err) {
    console.error(err)
  }
}

readFile()

In this example, the async keyword is used to define a function that contains asynchronous operations. The await keyword is used to pause the execution of the function until the asynchronous operation completes. The try...catch statement is used to handle errors that may occur during the asynchronous operation.

Which one should you use?

Promises and async/await both provide a way to handle asynchronous operations in JavaScript. The choice between the two depends on personal preference and coding style.

In general, promises are a good choice if you need to handle multiple asynchronous operations in parallel or if you need more fine-grained control over the flow of the asynchronous code. Async/await, on the other hand, is a good choice if you are writing code that needs to be more readable and maintainable, or if you are working with a codebase that already uses async/await extensively.

When using either promises or async/await, it is important to follow best practices and standards to ensure that your code is readable, maintainable, and efficient. Here are some tips to keep in mind:

• Always use the catch() method to handle errors that occur during asynchronous operations.
• Use Promise.all() to execute multiple promises in parallel.
• Use async and await as sparingly as possible to avoid creating overly complex code.
• Use descriptive variable and function names to make your code more readable and maintainable.
• Use a consistent coding style, such as the Airbnb JavaScript style guide, to ensure that your code is consistent and easy to read.