JavaScript - Best Way To Study Js?

For me, Javascript is not like HTML, while I am understanding almost everything I am reading so far, some things and some codes don't really make sense to me, I really don't know how to explain this, it's like I will understand every part of a code while studying it but if I were asked to write the code I will have difficulty. I remember some designers in the past saying they could not understand it too well so they simply copy codes for whatever purpose they desire but I don't want to do this so how can I make JS studying better please?