How to Check if a WebSocket Is Connected in JavaScript?

You can check if a WebSocket is connected by doing either of the following:

  • Specifying a function to the WebSocket.onopen event handler property, or;
  • Using addEventListener to listen to the open event.

For example, you would use the event handler property like so:

const ws = new WebSocket('ws://localhost:8080');

ws.onopen = function (event) {

Or, as an alternative, you could use addEventListener (to listen to the open event) like so:

const ws = new WebSocket('ws://localhost:8080');

ws.addEventListener('open', function (event) {

The open event is fired when the connection with a WebSocket is opened. When this happens, the readyState of the WebSocket connection changes to OPEN.

This post was published by Daniyal Hamid. Daniyal currently works as the Head of Engineering in Germany and has 20+ years of experience in software engineering, design and marketing. Please show your love and support by sharing this post.