Box Staff Software Engineer, Front End interview questions

Guidance received was to be prepared for to code real world application using vanilla js. As soon as the interview began the interview start shooting backend questions and then one js question. Highly unprofessional- the interviewer was complaining how he hates to taking interview and wants to move into management roles instead. At the end of interview I gave some feedback he mentioned he was not aware he was interviewing me Frontend role. These people do understand the effort candidate puts to come prepared as per the guidance and skills, waste of time.🤦🏻‍♂️