Prompt when writing a quick reply

Several times I have been writing a quick reply and then accidentally hit big red "Reply to Thread" button rather than the little orange "Post Quick Reply" button, thus losing everything I had just written.

Would it be possible to display a prompt when you try to navigate away from the page after entering something into the quick reply text box? There are many websites who have similar prompts to stop you losing your message and I think it would be nice if this website had something similar.