3 phases:
1) Recruiter: General questions about history and also general Javascript questions.
2) Video interview with Engineer: Using coderpad to answer several javascript questions: general JS interview questions, flatten an array w/o built-in methods, and binary search.
3) In person 3 hour whiteboard interview: Make sure to study algorithms and data structures. This part of the process is similar to a Google or Facebook whiteboard interview. Each hour was spent with 1 or 2 engineers. Flatten an array, Binary search, recursion, general Es6 questions, general React/Redux questions, etc.
In general, the overall process was quick. The only thing that was nerve racking was the whiteboard interview. The engineers helped and pointed me in the right direction when I would get stuck. The role required react/redux knowledge, but only got like 2 or 3 questions about it.
This was by far the toughest interview I have ever had for a front end dev role. I didn't get the job, probably because I was nervous and my brain was fried just thinking about the 3 hour interview itself. There were some questions that had obvious answers that I completely missed.
Make sure you study and mentally prepare yourself to get grilled! Practice, practice, practice.