Question

Is there anyway with jQuery to pop up a message to the user that the database record that they are in, has been changed and that they need to refresh in order to pick up changes?

So basically, if they are viewing a record, walk away and then come back, where the user is presented with a message that the record they are currently viewing has changed, and that they should refresh the page?

Answer 1

Sure, this very site does it.

How it roughly works:

1. Using setInterval and $.ajax(), the client polls a backend script ever X seconds.
2. The backend script checks the database and returns some sort of data – JSON is likely preferable in this case – indicating whether or not
3. On the client side, the JavaScript parses the response from the server and acts accordingly.

Some caveats:

• If there is any sort of traffic, this has the capability to bring a server to its knees. Take great care when determining the frequency of the polling.
• I suggest limiting the total number of times per page load that the script is able to poll the server (e.g. after 20 times, the script stops polling). This way, you won’t waste cycles when users leave the page loaded in their browser and walk away, for example.

Alternatively, you could look at Comet, which is more technically difficult and requires a great deal of server setup/sysadmin type knowledge to get working properly.