Thanks for the report. It should be fixed now.

First time submitting an issue, hope I'm not going about it the wrong way.

Final fixed test recipe is:

{ oil: '3 tbsp', flour: '2 cup', sugar: '0.5', milk: '1 cup' }

'Sugar' has no unit. Instructions don't seem to cover missing units.

You can bake a basic cake is using the following ingredients

Corrected:
You can bake a basic cake by using the following ingredients

.

Fixed, thanks!

All other are seprated by a space but

 "milk" : randomArr[3] + "ml"

A classical question for an interview job and very important to know it. Unfortunately it's a duplicate of a kata previously published: https://www.codewars.com/kata/find-the-duplicated-number-in-a-consecutive-unsorted-list-tougher-version

And many others with very similar.

Description specifies two different rules for which duplicate to return. The second is wrong.

Returning -1 is not a good choice. It might be a valid return value as well ( you never specify that the array only contains nonnegative numbers ). undefined or in this case maybe NaN (!) might have been better choices, if you don't want to throw an Error.

map[] === true ( in the reference solution ) is a bit of an antipattern, isn't it? It's a Boolean already.