Interesting, this is a bug.
For the scene editor, we run the head html through a tidy process to ensure that mangled head html code won't interfere with editing. (Of course valid head html still can in many other ways!). The tidy method we use isn't smart enough to know about the <script> tag, and so is converting the for loop from:
for (i = 0; i < divs.length; ++i) {
to:
for (i = 0; i < divs.length; ++i) {
This is invalid javascript, and therefore failing.
I thought this could still be done? Regardless, this is how I investigated:
defaults write com.tumult.Hype4 WebKitDeveloperExtras -bool YES