Maybe you can try making small code snippets that you think 'summarizes' what you have learned on that chapter and which you can reuse and build upon and save them in a folder in your harddrive?
Agreed. These days I usually comment my snippets thoroughly and commit them to a git repository. If I need something more than that or they're not web-related I'll put them in OneNote. If they are web related but I want demonstrations included then I put them into CodePen.
+1 for git, why keep it on disk? n Github, other devs can see it, you can see it when away from your disk, recruiters can see it, and it's less likely to get lost!