This is nothing against uglify. Rather, here's the story on this:
Commit e4cd1e fixed an error that was causing minified files to break in IE.
This was due to how IE interprets things, not how UglifyJS was minifying them.
Indeed, Closure Compiler had the exact same problem.
The decision to move to Closure Compiler was due to a variety of factors, which
came down to primarily feature set and tests. Closure Compiler is well tested
and maintained. It also includes a number of additional, beneficial features.
UglifyJS is an excellent project and I would recommend it to anyone, but it is
not tested (no unit tests; it's tested by ensuring common libraries like jQuery
run after minification). It is, however, significantly faster.
It's likely that, in the future, once I add autoconf for the build process to
configure certain settings, that I will add UglifyJS as an option. I'm sure many
people would prefer that, especially those who dislike Java and do not wish to
have it installed. Hopefully those that do decide to install Java will go with
openjdk, not Oracle's proprietary implementation.
Ah - you have to love those "ah-ha!" moments. The issue here is that both
uglify-js and closure compiler mangled the names in such a way that the var and
the function name had different values. In the case of closure compiler, the
function name was used to instantiate the constructor if the 'new' keyword was
omitted. This worked fine in all other tested browsers, but IE handles it
differently.
This little experience was rather frustrating. Indeed, it would imply that
the static implementation (at least, accessing protected and private static
members) was always broken in FF. I should be a bit more diligent in my testing.
Or perhaps it broke in a more recent version of FF, which is more likely. The
problem seems to be that we used defineSecureProp() for an assignment to the
actual class, then later properly assigned it to class.___$$svis$$.
Of course, defineSecureProp() makes it read-only, so this failed, causing
an improper assignment for __self, breaking the implementation. As such,
this probably broke in newer versions of FF and worked properly in older versions.
More concerningly is that the implementations clearly differ between Chromium
and Firefox. It may be that Firefox checks the prototype chain, whereas Chromium
(v8, specifically) will simply write to that object, ignoring that the property
further down the prototype chain is read-only.
Mike Gerwitz