Personally, what I felt while taking the lecture is that if JavaScript is not your main language, you may have some difficulty understanding the advanced data structures. I heard that even if you don't know JavaScript well, the lecture proceeds only with basic grammar, so I listened to the basics first and then the advanced ones. The basics were okay because I implemented simple structures, but the content covered in the advanced ones was not. I don't know if it's because of the characteristics of this language or the complexity that arises from implementing only basic grammar, but when connecting the methods required to implement a certain function, I have thoughts like 'Is this function connected to this behavior?' or 'This behavior?', so it's hard to understand. I think it's because each language has its own unique programming style, and I'm not familiar with it. In my case, I'm familiar with Python and Java, so when I studied the data structures explained in Java, I was able to clearly picture the logic of how the logic is implemented in my head. If you're proficient in JavaScript, you'll be fine!