如何实施实时表单编辑，就像Google Docs一样

Question

I am trying to add the feature that Google Docs has, which is real time collaboration, to an editable textarea in HTML. For example, this would allow 2 or 3 users can edit the same textarea collaboratively. How would one go about approaching this problem, or is there is a JavaScript library that can be used? (I use PHP, mySQL, and JavaScript/AJAX/jQuery).

Answer 1

In order to facilitate real-time updates between more than one Web client, you'll need to use a technology that either capitalizes on the request/response cycle of the Web by using a Comet or Websockets solution.

To keep the textarea updated, you'd need to establish a long-lived HTTP connection or a Websocket connection to your server from all 3 clients. Each textarea would need a keyup or keypress handler that, when invoked, sends the character across the stream to the server. When your server retrieves this data, it would then need to return a response to the other 2 connected clients.

The response would need to then be handled by updating the value property of the textarea with the most recent data.

I see you're using PHP, which I do know supports comet. You'll need to setup comet (or Websockets) in order to implement such a solution.

With that said, a more rudimentary alternative would be to use polling to achieve the desired effect. This would involve all 3 clients making requests to the server periodically to retrieve updates. As you can imagine, the faster the polling rate, the more real time the application would feel. However, with a faster the polling rate, your application would consume more bandwidth and resources.

For 3 clients, this may be feasible, but for any serious application that involved heavy usage, you would definitely want to look into Websockets or Comet.

To answer your question of JavaScript libraries, check out the Dojo Cometd library for a Comet solution on the client-side.