Oh I just realized, you have to run the first three lines by themselves, and then call the last line on a separate command. I didn’t realize that at first, as I assumed that everyone would type the commands one line at a time.
I’ll edit the article to reflect this. I should be able to explain more technically why it doesn’t work when you paste the lines all together, but basically, the script that the code is creating isn’t in the DOM until you execute the commands, so you have to execute the last line separately.