turn on ascii_only for issue with emoji and regex

[viankakrisna]

Fixing #2488
Verified the changes by cloning https://github.com/crabicode/create-react-app-emoji and manually editing react-scripts/config/webpack.config.prod.js
Before:

After:

[gaearon]

Do we need to report a bug to Uglify?

[viankakrisna]

The question is why did they have that option in the first place and not turned on by default? I'll try to dig more on that.

[viankakrisna]

mishoo/UglifyJS#171 I think they do that because it affects bundle size.

[viankakrisna]

it also suggests that <meta charset="utf8"/> on index.html would fix that. we have <meta charset="utf-8"> on public/index.html

[gaearon]

If we change it to remove dash does it work? Then I'd prefer to do that.

[viankakrisna]

it doesn't work when I remove the dash

making it uppercase also not working

There are 32 issues related to ascii_only and special characters in uglifyjs2 repo https://github.com/mishoo/UglifyJS2/search?p=1&q=ascii_only&type=Issues&utf8=%E2%9C%93
So I think it's better to turn it on. If we want to file issue, maybe to turn it on by default?

[gaearon]

Thanks!