HackerRank's "Solve Me First" is the first problem everyone does. Ours is "Copy Me First": return a deep copy of the input. Returning the input itself is a wrong answer, and also a partnership.

The editor runs your JavaScript in the browser against 2 sample cases (Run Code) and 5 hidden cases (Submit Code), including a reference-equality check so return a fails the way it should. Line numbers, tab handling, the green Submit button, the right rail with Author/Difficulty/Max Score/Submitted By, the star rating. No login wall, which is the one thing HackerRank should copy from us.