Some people would argue that optional static typing (flow/typescript over js style) can be superior because you get the best of both worlds - typing when you n

Some people would argue that optional static typing (flow/typescript over js style) can be superior because you get the best of both worlds - typing when you need it and no typing where it's not necessary / you need to prototype it quickly. There is some merit behind it because more often than not, you don't know in advance what class hierarchy you're going to end up with. No typing means faster prototyping and you have flexibility to add it at your own paste.