String to prompt a user with when spooling (or a download originated by a PrintHTML call) is still in progress but the page is being closed or navigated away. By default, ScriptX waits 5 seconds in blocking mode to let spooling complete, then prompts the user with the choice to cancel the printing process. The user may decide to wait for another 5 seconds, and so on.
Note: to suppress the prompt you can force the blocking wait state with WaitForSpoolingComplete after any Print or PrintHTML call or before leaving the page. However the use of WaitForSpoolingComplete() after each PrintHTML call in a sequence of calls is not recommended. Use it only after the last call in the sequence.
This is a read/write property.
printing.onbeforeunload = string
Check out the source code of the ScriptX Using WaitForSpoolingComplete sample.