JavaScript & JQuery, Chapter 1 by Jon Duckett

How do I read JavaScript & JQuery, Chapter 1 by Jon Duckett? I go to the website link, but I suppose I need to buy the book in order to able to read the content?

Yes you would need to purchase the book (but it’s optional reading for the course).

Luckily there are many freely available quality resources online.
I personally like the book Eloquent Javascript (of the free ones): https://eloquentjavascript.net/