Code snippets, exercises, sample chapters, etc are available on GitHub repo [3]

You can also get the book as part of free bundle [4]

[1] https://gumroad.com/l/js_regexp

[2] https://leanpub.com/js_regexp

[3] https://github.com/learnbyexample/learn_js_regexp

[4] https://leanpub.com/b/regex