optimized/minifed javascript code but still readable/maintainable
No, it's not a coding style (except if you're doing code-golfing manually for fun).
You take the unminified code and squeeze it through a tool such as https://github.com/terser/terser (which is probably the most popular at the time of writing).
You can see what Terser does online with their Try Terser tool. https://try.terser.org/