Beyond Forms: Exploring Alternative Methods for Real-time Updates in Htmx

Enabling the Extension

To activate the WebSockets extension on an element, you use the attribute hx-ext="ws".

Connecting to the Server

The ws-connect attribute specifies the endpoint on your server that handles WebSockets. For instance, ws-connect="/notifications" defines the /notifications endpoint as the connection point.

Receiving Messages

The server can send messages to the connected client. Htmx parses the received content as HTML and replaces the element's content based on the id property of the received HTML. This is similar to Htmx's Out of Band Swaps functionality.

Example

Imagine a chat application built with Htmx and WebSockets. The server might send a new message as HTML containing the sender's name and message content. Htmx would then replace the content of a designated element (like a chat window) with the received HTML, effectively displaying the new message.

HTML (client-side)

<!DOCTYPE html>
<html>
<head>
  <title>Htmx Chat Example</title>
  <script src="https://unpkg.com/[email protected]"></script>
</head>
<body>
  <div id="chat-window">
    </div>

  <form hx-ext="ws" ws-connect="/chat">
    <input type="text" name="message" placeholder="Enter your message">
    <button type="submit">Send</button>
  </form>

  <script>
    document.querySelector('form').addEventListener('submit', (event) => {
      event.preventDefault(); // Prevent default form submission
      const message = document.querySelector('input[name="message"]').value;
      document.querySelector('form'). hxPush({"message": message}); // Send message via Htmx
    });
  </script>
</body>
</html>

- We have a div with the ID chat-window to display chat messages.
- A form with hx-ext="ws" enables the WebSockets extension.
- ws-connect="/chat" specifies the server endpoint for chat communication.
- An input field for the message and a submit button.
JavaScript
- We prevent the default form submission using event.preventDefault().
- When the form is submitted, we grab the message from the input field.
- We use document.querySelector('form').hxPush({"message": message}). This sends the message data (message) through Htmx to the connected WebSocket endpoint (/chat).

Server-Side Implementation (dependent on your server-side language)

It should broadcast the received message to all connected clients.
The server should handle the /chat endpoint and process incoming messages.

Receiving Messages

When the server broadcasts a message, the client receives it as HTML. Htmx parses the HTML and replaces the content of the element with the ID matching the received HTML's id attribute. In this case, the chat-window element would be updated with the new message.

- SSE allows the server to push updates to clients without requiring a full WebSocket connection.
- Clients establish an HTTP connection that remains open, and the server can send updates at any time.
- Htmx provides built-in support for SSE using the hx-sse attribute.
Long Polling
- This technique involves the client repeatedly sending requests to the server, simulating a real-time connection.
- The server holds the request open until it has new data, then sends a response.
- Htmx doesn't have direct support for long polling, but you can implement it using vanilla Javascript or libraries like Axios.
Web Workers
- Web workers are background scripts that run independently of the main thread.
- You can use Web Workers to establish a separate WebSocket connection and handle updates in the background.
- This approach can improve responsiveness as the main thread isn't blocked by waiting for WebSocket messages.

Choosing the Right Method

The best method depends on your specific needs:

Fine-grained Control
Web Workers provide more control over the communication logic and can be useful for complex applications.
Scalability
SSE might be preferable for high-traffic scenarios due to lower server overhead compared to WebSockets.
Simplicity
Htmx WebSockets offer a straightforward solution for basic real-time needs.