They interviewed me on JavaScript fundamentals. I guess I would recommend brushing up on JS frameworks and such. They were very kind and patient, and answered any questions I had about the company.

Beware of the "All Levels" in the title, they are looking for mid-senior level experience. (Heard from other friends in the field) Interview consists of general interview questions as well as technical questions. However one of the interviewers was quite rude as they laughed at one my answers which shattered my confidence during the interview. Overall just a general interview, but not the company I was looking for.