Grade: Meets Expectations

I think this feature request is pretty well done. I really liked the idea - it was unique and well thought. The technical design is pretty good aside from a couple of potential problems surrounding state mutation. The caveats section was really good work and met all the expected requirements for a professional level caveat section of a feature request.

Nice job!

I like this background! It details why the feature is important and the idea is good as well. A lot of applications in a similar format presently are similar to this interaction. I think you've given a lot of good reasons as to why it should be implemented including what it can prevent. Good work!

The technical design is also very nicely formatted, well explained and detailed. It provides a step by step instruction as to how it would be implemented which is great to see. A couple notes about state mutation: Inside of this function, a variable should be created and set equal to this.state.playlist.. In React we don't want to mutate the state directly or indirectly. Since arrays are reference types, if you were to change the variable that you've set equal to this.state.playlist, it would update it's reference as well. You can double check this using console.log. In the scenario you would want to make sure to create a copy of this.state.playlist rather than just storing it in a variable. You can read more about this on the official react documentation here: https://reactjs.org/docs/react-component.html#state

By avoiding updating the state directly or indirectly, we can maintain more predictability about our applications state.

Excellent! This is similar to the line of thinking I had when I was reading about your idea. It's really good to see that you provided a backup plan if this were to be too big of an issue. The implementation details are pretty straight forward, and the mention of running time & performance was a good additional mention. As for the additional updates to state, using CSS to hide the element is a pretty common technique as it doesn't require you to constantly update the DOM.