This brings up something, I have wanted for a while. Something similar to about:config in FF, but is just enable/disable for every javascript API. An additional thing would the ability to make certain API always return a certain value, or write my own dummy function in JS to get around breaking sites.

Like some things I can disable in FF in about:config, but others I can not. Otherwise, I have to modify and compile FF and hope I don't break any extensions I use.

A similar thing would also be nice for HTML elements.