Complete introduction to async functions and ES6 modules in Node.js (2024)

FAQs

How to define async function in ES6? ›

Creating async Function

An asynchronous JavaScript function can be created with the async keyword before the function name, or before () when using the arrow function syntax. An async function returns a promise.

ES6 or ECMAScript 6 is designed for JavaScript language standardization. Using import statements in Node. js would earlier give an error, but after enabling ES6, we can easily use import statements in Node. js.

Async is a utility module which provides straight-forward, powerful functions for working with asynchronous JavaScript. Although originally designed for use with Node. js and installable via npm i async , it can also be used directly in the browser. Async is also installable via: yarn: yarn add async.

Using async in ES6

An async function is a function that knows to expect the possibility of the await keyword being used to invoke asynchronous code. If we were to type the following lines into the browser's JavaScript console, it would immediately print “Hello“: const hello = () => "Hello"; hello();

The asynchronous function can be written in Node. js using 'async' preceding the function name. The asynchronous function returns an implicit Promise as a result. The async function helps to write promise-based code asynchronously via the event loop.

The async keyword marks a function as asynchronous, and the await keyword allows for pausing execution until a promise is resolved. Let's dive into a more elaborate example : In this example, the code reads sequentially, making it easier to follow the flow of asynchronous operations.

The primary difference between CommonJS and ES Modules is the module loading system. CommonJS uses synchronous loading, while ES Modules uses asynchronous loading. Additionally, CommonJS uses the require function to import modules, while ES Modules uses the import statement.

Modules make it easy to maintain the code, debug the code, and reuse the piece of code. Each module is a piece of code that gets executed once it is loaded. Modules in ES6 is an essential concept. Although it is not available everywhere, but today we can use it and can transpile into ES5 code.

The word “async” before a function means one simple thing: a function always returns a promise. Other values are wrapped in a resolved promise automatically. So, async ensures that the function returns a promise, and wraps non-promises in it.

When to use async in nodejs? ›

Use async / await in Node. js when you want to write asynchronous code that is more readable, sequential, and better at error handling. This approach reduces the cognitive load for developers, making it easier to understand, read, and debug the code.

In Node. js, the require function is used to load and import external modules into your application. By default, it operates synchronously, which means that the script execution is blocked until the module is loaded completely.

ES6 or ECMAScript 2015 is the 6^th version of the ECMAScript programming language. ECMAScript is the standardization of Javascript which was released in 2015 and subsequently renamed as ECMAScript 2015.

Callbacks are the traditional way of handling asynchronous operations in Node JS. A callback function is passed as an argument to an asynchronous function and is executed when the operation completes.

The async keyword transforms a regular JavaScript function into an asynchronous function, causing it to return a Promise. The await keyword is used inside an async function to pause its execution and wait for a Promise to resolve before continuing.

Use async Keyword: Prefix the function declaration with the async keyword to indicate that it is an asynchronous function. Specify the Return Type as Promise<T> : Specify the return type of the function as Promise<T> , where T is the type of the resolved value.

async functions in javascript are marked with the keyword async and inside these async functions, we write promise-based code as it was synchronous. We just need to use the await operator whenever a promise is returned. This operator halts the execution of the current function until the promise is settled.

Need to convert a function that returns a Promise to an async function that uses the async/await syntax? Place the caret on that function, press ⌥⏎ (macOS) / Alt+Enter (Windows/Linux) and select Convert to async function.