Firefox 4 onBeforeUnload custom message

Question

In Firefox 3, I was able to write a custom confirmation popup with:

window.onbeforeunload = function() {
   if (someCondition) {
      retur         


        

Answer 1

From MDN:

Note that in Firefox 4 and later the returned string is not displayed to the user. See Bug 588292.

This "Bug" is actually a (imho questionable) feature.. so there's no way to display the message in Firefox 4. If you think it should be changed, comment on that bug so the Firefox developers will know that people actually want to be able to show a custom string.