Is it necessary to have knowledge of JS before starting this course?

You can pursue the Datastructures and Algorithms course by UCSD and HSE on Coursera. It has a set of problems of varying difficulty every week and is a good learning experience from a competitive programming perspective! I've done the first course and can vouch for the problem quality though some lectures are confusing and I had to consult some extra material for understanding though that is okay considered they have 4-5 different instructors.

Data Structures and Algorithms