Production build does not work for Safari 10 due to Safari bug. Fix available.

[satyavh]

There's a bug in Safari 10, it throws on uglified code
https://bugs.webkit.org/show_bug.cgi?id=171041

There's a fix as well, but Create React App does not implement the fix
https://github.com/mishoo/UglifyJS2/tree/harmony#mangle-options

The result is that it is very likely that a production build created by npm run build does not run on Safari. At least ours does not (mvp.giveth.io)

How to update the uglify settings?

[Timer]

I'm not sure I understand; Safari 10 throws on very specific minified code (based on the issue you linked).

That specific code being a for (let a of ...) { ... }; we don't support minifying ES6 (i.e. let), so I don't understand how this flag would fix the error you are experiencing [because it can't happen in our setup].

Could you please put together a minimal reproduction case?
I'd like to understand this error more before flipping flags.

[Timer]

Are you ejected? What version of react-scripts are you on?

Please follow the issue template.

[satyavh]

No we didn't eject, but I got to the bottom of this and turns out we adjusted the react-script to support minifying ES6, by updating to "uglifyjs-webpack-plugin": "^1.0.0-beta.2"

Closing this issue now. Sorry for the confusion.
But now at least you know updating that plugin will break builds in Safari :-)