Unlike plain JavaScript files, JS-ERb files also allow the use of Embedded Ruby, which we apply in the create.js.erb fileto updatethefollow form with the unfollow partial (which is what should show after a successful following) and update the follower count. The result is shown in Listing 11.39. This uses the escape_javascript function, which is needed to escape out the result when inserting HTML in a JavaScript file.

With that, you should navigate to a user profile page and verify that you can follow and unfollow without a page refresh, and the test suite should also pass:

Using Ajax in Rails is a large and fast-moving subject, so we’ve only been able to scratch the surface here, but (as with the rest of the material in this tutorial) our treatment should give you a good foundation for more advanced resources.