There is a separate branch for ES2015+ here:
<a href="https://github.com/mishoo/UglifyJS2/tree/harmony" rel="nofollow">https://github.com/mishoo/UglifyJS2/tree/harmony</a><p>The new primary committer, alexlamsl, is good about responding to bugs & pushing out new versions fast:
<a href="https://github.com/mishoo/UglifyJS2/issues?q=is%3Aissue+is%3Aopen+label%3Aharmony" rel="nofollow">https://github.com/mishoo/UglifyJS2/issues?q=is%3Aissue+is%3...</a><p>But there is still no CHANGELOG. He is aggressive at updating the docs, so you'll have to look at diffs yourself.
You can handle es6+ with the harmony flag but if you're already using Babel is there any reason to use Uglify over Babili?<p>I believe Babili generates minified/mangled output directly from the Babel AST which would be way more performant during the dev cycle.
Support for pure annotations was added.<p><a href="https://github.com/mishoo/UglifyJS2/commit/1e51586996ae4fdac68a8ea597c20ab170809c43" rel="nofollow">https://github.com/mishoo/UglifyJS2/commit/1e51586996ae4fdac...</a><p>This will enable removing unused transpiled classes from e.g. Babel.<p>See <a href="https://github.com/mishoo/UglifyJS2/issues/1261" rel="nofollow">https://github.com/mishoo/UglifyJS2/issues/1261</a>
How much does these uglifiers slow down the code for a the client? Especially if you're using a mobile or slow arm machine? I started to think about these things when u started using an arm based chromebook. Stupidly bloated js heavy sites started to stand out. Facebook is unusable, slightly better if you disable extensions.