if you're writing functional code, you should already know what partial application is - and the "partial" function is only necessary in this case because JS is

if you're writing functional code, you should already know what partial application is - and the "partial" function is only necessary in this case because JS isn't a curried language by default. your idea of B being more simple is largely driven by the fact that you likely have more experience writing code in that manner. With experience writing functional code you should find that both A and B are clear at a glance.