Feature request: Add validator for custom hashes

[slavafomin]

Hello!

Thank you for this great library!

However, I would propose to introduce generic validator for different types of hashes. Right now, we have isMD5() validator, which is great, but there are no validators for other hash types, like sha256.

I would suggest the following API:isHash(str, algorithm).

We could call it like this: isHash('6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b', 'sha256').

Here's the list of most popular hash functions (algorithms): http://stackoverflow.com/q/16393650/1056679.

The original isMD5() could be deprecated over time in favor of isHash(str, 'md5').

What do you think?

Thanks!

[chriso]

Great idea.

It could be something simple like:

var lengths = {
  md5: 32,
  sha1: 40,
  sha256: 64,
  // etc
}

function isHash(str, algorithm) {
  return validator.isHexadecimal(str) && str.length === lengths[algorithm];
}

[chriso]

Fixed by #711.