Minified code is functionally identical and still "source" from the point of view of code execution - i.e. it is not compiled into a different language (e.g. from TypeScript or CoffeeScript, or to WebAssembly) nor is it transpiled into a different language dialect (e.g. from ECMAScript 2015 a.k.a. ES6 to 5th edition).
Beware, however, that minified code is not the "preferred source for editing, and therefore not "source" for the purpose of Debian packaging.
?UglifyJS 3 is the conservative choice: Has fewer reverse dependencies so more likely to be kept up-to-date and less likely to be problematic to backport.
esbuild - implemented in Go
shrinksafe - implemented in Java
yui-compressor - implemented in Java, inefficient, dead upstream