You don't need a queue.. Just issue the commands as the user makes them. Each command should be separate from every other command, so that order doesn't matter.
I think order does matter - lets say a user types in 'hello' and then saves the note, then quickly changes his/her mind and types in 'hello world' and saves the note. Now the backend will save the version of the note which it receives last, which could be 'hello' depending on network lag.
You should probably use some kind of versioning so that when you receive version 123 and the version in the database is 121, you won't commit 123 until you receive #122.
If the user deletes the note and the server receives the delete request before other modification deltas, simply ignore the deltas that arrive after the delete command.
In my opinion it's a lot more simple to solve this kind of problems on the server side of a web application.
How does one abort the previous request unless a queue is being kept track of? Also, there could have been a few other requests made between the first save and the second save. Its definitely possible I'm just not understanding how XMLHTTPRequest objects work - please do explain if you think that is the case.
Also - I'm not necessarily using XMLHTTPRequest, I'm leaning towards dynamic scripting as my site will need this widget to run across several different subdomains - dynamic scripting doesn't have a lot of the nice status functionality that XMLHTTPRequest does...
When a user needs to save their note
If the note is already saving
Set note.saveAgain = true
else
Start the process of saving the note
When the note has saved
If note.saveAgain == true
Set note.saveAgain = false
Start the process of saving the note again
That doesn't require a queue. It also only saves the most up to date version.
