dpaste and warning upon leaving page

[Anonymouse via Digitalmars-d]

I just had a PEBCAK moment where I was composing a large-ish 
snippet on dpaste, then accidentally left the page by clicking 
the back button on my mouse. Going back to the page I see my 
changes were lost.

Could we maybe add a warning when leaving the page if the content 
has been changed? I think it's the onbeforeunload event, but I 
don't know javascript well.

http://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_onbeforeunload_dom