I found that it was useful to have a place to keep track of the state (enabled or disabled) of certain buttons, which I could use to determine whether a button state should be enabled or disabled. For example, in the play() and pause() functions below, the "play" button may or may not be disabled/enabled for more than one reason. Without this, the only way to determine if the button is disabled would be to run some jQuery to see if the "disabled" div is there or not, which seems like a more expensive, and less elegant solution. Since I was doing this for the play/pause, next, and previous buttons, I extended it to the other buttons as well - but I could remove those that are not currently being enabled/disabled in the code.

If you would prefer to handle this in a different way, please let me know.