I remember (it seems...) there was a way, maybe some config option, to combine/merge javascript files (for production sites). I mean just with vanilla wordpress code, not plugins.
Am I wrong? If not, how to? Can't find reliable infos.
Topic wp-config configuration Wordpress javascript performance
Category Web
I prefer separete all my front-end assets from the back-end, so I use Gulp to manage (compile, mifify etc..) all my assets.
But if you want to use Wordpress I found this article. I did not test the code, but by just reading and seeing the comment section I think that will work for you.
But I really recommend you to use something Like Gulp, Webpack or Yarn to manage your front-end assets.
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