Mutations regex not working on one test (but the regex is correct!)

Tell us what’s happening:
mutation(["hello", "Hello"]);
Returns false, it’s the only test that fails.

I have tested this regex on, using /[Hello]/gi as the regex and hello as the test and it matches no problem.

If I change my code to
return /[Hello]/gi.test(arr[0]);

Then it passes that test.

Why is it failing when I use the array reference in the regex?

Your code so far

function mutation(arr) {
  return /[arr\[1\]]/gi.test(arr[0]);

mutation(["hello", "hey"]);

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.106 Safari/537.36.

Link to the challenge:

Your code is not correct. Here you can see it running the test that fails: