Meta Frontend Engineer interview questions

Communications first occurred with a 30 minute phone screening to determine if I would be a good qualifying fit. From there, I was contacted with instructions to complete a programmatic challenge to be written in JavaScript that was estimated to take between 8 and 10 hours time as solved by current Facebook employees. The challenge, at it's core, was intended for candidates to prove their programming chops. Facebook was looking for both succinct and optimized solutions, i.e. you better use the most efficient algorithm available while still maintaining very few lines of code. The problem I was asked to solve looked fairly easy at face value, but I soon realized a few hours in that there were numerous edge cases that needed to be accounted for and would drastically reduce my algorithms efficiency due to nested loops. I solved the problem with a sub-optimal solution in around the time required but was denied continuation of the interview process. I wasn't given any real feedback, but I didn't ask for it either. The recruiter was very pleasant on the phone and in his emails.