Ruby also has this. e.g. you can use send to call private methods during testing (and then use static analysis like rubocop to ensure only public_send is used i

Ruby also has this. e.g. you can use send to call private methods during testing (and then use static analysis like rubocop to ensure only public_send is used in production). You also can simulate it in JavaScript by using a closure and a separate package for your "private" functions. By mixing the "private" code into the closure you can make it private in usage but still available to unit tests.