It is hard to learn a language without any knowledge before, but because you know how to program in Python it should be not that hard to learn the fundamentals of JS. In the most languages, the logic is the same.
Is Python losing popularity?
Overall, Python remains the third most popular language behind C and Java in the January 2021 edition of the index, which is based on a formula assessing searches in popular search engines. Python had leapfrogged Java for second place in the November index but fell back to third place in December.