To start as a couple of others have already pointed out you haven't implemented all the criteria. If I was evaluating your solution based on what they are aski

To start as a couple of others have already pointed out you haven't implemented all the criteria. If I was evaluating your solution based on what they are asking for I would have passed on you as well. Your solution is unnecessarily complex and over built. They are asking if can you use JS to manipulate a select box. Not including tests you have brought in 400+ lines of code (184 lines of code + the EventEmitter library) to implement 75% of the functionality you were asked for. That is a lot of code to take an item from a select box and add it to a list. Knowing that developers leave I would not want to inherit a solution like this. To put it in car terms you built a 911 when the customer was asking for a vw bug.