I dont understand what you mean. Are you saying that in C you only calculate the first few digits of the hash? That's not how sha256 works.

Edit: oh i think you mean in c the string comparison short curcuits. I would expect the same to be true in javascript too. Its true in most languages.

Maybe you are just worried about general language overhead, which is a fair point. Is the anubis check even using multiple threads? For the c case, the real benefit wouldn't be if you can use C, but if you can use the GPU.

The whole thing is kind of silly though. SHA256 is a terrible choice of hash for PoW. They should be using argon2 or something memory heavy.