WebSocket in JS

WebSocket is a protocol that allows for real-time communication between client and server over a single, long-lived connection. Unlike HTTP, which uses a request-response model, WebSocket enables bi-directional communication between the client and server in real-time.

JavaScript is a popular language for building web applications that require real-time communication, making WebSocket an important technology to learn for web developers.

To use WebSocket in JS, you first need to create a WebSocket object using the WebSocket constructor, passing in the URL of the WebSocket server as a parameter. For example:

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

Once you have created a WebSocket object, you need to add event listeners to handle the WebSocket events. Here are the events that we can handle:

• **open**: This event is fired when the WebSocket connection is established.
• **message**: This event is fired when a message is received from the WebSocket server.
• **error**: This event is fired when an error occurs in the WebSocket connection.
• **close**: This event is fired when the WebSocket connection is closed.

socket.addEventListener('open', (event) => {  
  console.log('WebSocket connection established');  
});  
socket.addEventListener('message', (event) => {  
  console.log('Received message:', event.data);  
});  
socket.addEventListener('close', (event) => {  
  console.log('WebSocket connection closed');  
});  
socket.addEventListener('error', (event) => {  
  console.error('WebSocket error:', event);  
});

To send a message from the client to the server, you can use the send() method on the WebSocket object:

const message = 'Hello, WebSocket!';  
socket.send(message);

To receive data from the server, we need to handle the **message** event of the WebSocket object. Here's an example of how to receive data from the server:

socket.addEventListener('message', function(event) {  
  const message = event.data;  
  console.log('Message received: ' + message);  
});

On the server-side, you can use libraries like ws or socket.io to handle WebSocket connections in Node.js.

WebSocket is a powerful technology that enables real-time communication between client and server. With JavaScript, you can easily create WebSocket connections and handle incoming messages and errors.