The technical assessment consisted of implementing a component from a jQuery-based framework they use. It was in-person and it was after an interview with hiring and project manager.
The assessment was around 30 minutes to a 1 hour (I can't remember). I was given the opportunity to read through documentation to help me implement the component. It was rather smooth. The only downside is an HR representative is sitting next to me during my assessment, which I found a little strange.