Nodejs Promises

Nodejs Promises

In Nodejs Promises is an object that represents the eventual completion (or failure) of an asynchronous operation.

Promises make asynchronous code:

• Cleaner

• Easier to read

• Easier to manage

• Avoid “callback hell”

What Is a Promise?

A Promise has three states:

Basic Promise Example

Using Promises with Async Functions

Node.js provides promise-based APIs (like fs.promises):

Example: Reading a file with Promises

Promise Chaining

You can chain multiple .then() operations:

Handling Errors in Promises

Errors are handled using .catch():

Promise.all()

Runs multiple promises at the same time and waits for all to finish.

Output:

Promise.race()

Returns the result of the first completed promise:

Output:

Why Use Promises in Node.js?

✔ Avoid callback hell
✔ Better error handling
✔ Cleaner asynchronous code
✔ Works perfectly with async/await

Promises vs Callbacks