Absolutely. No need to change the kata - just thought you might want to know.

'Position of alphabet' should instead be 'Position in alphabet'.

You should remove the semicolon at the end of your function declaration.

As is, the kata seems to suggest that the tax is the actual tax due and simply asks you to add it to the subtotal. What you are actually giving is the tax as a percentage. The tax due needs to be calculated using the tax given as a percentage and the subtotal and only then added to the subtotal. Explaining this would make things much clearer.

It is unclear what is expected? What is supposed to serve as the secret when creating the hmac? What is supposed to serve as the data?

Variables in JavaScript should use lower camel case, not snake case - i.e. you should have "initialValue" and "finalValue", not "initial_value" and "final_value".

You might want to add at least a slight twist on this exercise. As it is, it's almost purely arithmetic. Even for a kata of 8 kyu, it seems a bit light on language features.

In the tests that are initially given, you use double equals where you clearly intend to use the assignment operator to set the color and then the state in order to test them.

You should use either 'buy' or 'Buy' in both the tests and the description but not both.

The way you have some of the tests set up don't seem to make much sense. You never use the second parameter when calling the search method and it's a little unclear how the second param is supposed to be used. You also want the search method to return the value of the node that you're searching for rather than the node itself, but this doesn't make much sense most of the time since you need that value to find the node in the first place, so that search is really functioning like a hasNode method.

I don't think you need the uncommented note at the top of the code, though of course you can keep it if you like.

I would include an example like the one you have in the test in the main description.

Everything worked well for me. I'd say 6 kyu seems about right, although I have no idea how to mark an estimated rank.