You are mutating the string in-place

learned

Fewer lines of code isn't equal to good/best code though. Readability matters a great deal in large codebases with all sorts of developers coming in-and-out on projects.

Great readability.

Still a duplicate.

The description and test cases have been updated to no longer request an output of "Blackjack!" but instead just request 21, to better match the rules of Blackjack

This was a problem in the random testing that has now been fixed, good catch

Sometimes the random tests give 11 as a value in the hand. But shouldn't it be always be 1 if it's an ace?

This is a duplicate of: https://www.codewars.com/kata/534ffb35edb1241eda0015fe

Also, a blackjack is when a player gets a 10-value card and an Ace as their starting pair. If a player ends up with 21 any other way, it's not a blackjack.

Not true, you're mutating the input, that's why.

Python basic tests require output as an Integer while the random tests require output as a string. I had to hardcode my solution to match the poor testing.

I got stuck with this problem. I have a very few ideas about functional programming in javascript.
Can you possibly show the solution on codepen or github or wherever you're comfotable with?
Thanks in advance.

There're already katas asking to generate some random output, and they're much better authored than this.

test.expect((7 <= dice_roll(7, 4927) <= 5*4927) == True, "Your solution didn't roll a possible value")

This test is wrong.