I think the description should include the number "100" in the number_of_duplicate_digits(3) example.

Description is incorrect for JavaScript. The tests always require two decimals, even for 0 and 1, which directly contradicts the description. In addition, the tests expect strings instead of numbers.

The easiest way to see the difference is to do both solutions for some smaller inputs by hand.
If you're confused about the function you've used, try to write it out as a loop and compare the differences.

JavaScript fixes

• Updated to chai
• Added anti-cheat (taken from here)

Resoved issues (at least for JS): 1, 2, 3, 4, 5

The array size is known and fixed. This runs in O(1).

Your solution is built around specific test cases. Try to take a more generalized approach.

Fixed

Fixed in Java, Crystal, and R. If there are any other languages that generate tests with less than 4 numbers, let me know.

Fixed the Java tests so they no longer generate incorrect ones.

Added some

As this is not a performance kata, I feel like the random tests are too hard. Several solutions time out and most solutions take more than 7 seconds to run.
I'd keep the random tests in line with other languages. For example, Java and Python have 40 tests with a 1-8 letter word.

The description fails to mention that the arrays in the solution should only contain unique values.

Many issues in JavaScript:

• No fixed tests in full test suite
• Random tests use global variables
• Random tests potentially generate only 1 test
• Random tests potentially generate infinite tests and times out (or exceeds buffer size)
• Random tests print to console
• Tests do not follow general kata coding guidelines and are hard to read
• Node 18 should be enabled
• Chai should be used for assertions