It’s because of the jQuery version you use. https://code.jquery.com/jquery-3.1.1.slim.min.js
slim version of jQuery does not contain all the original jQuery functions.
You should use a full version. You can download it from here.
It will help to better understand if you read this article from
here where at some point in it you will find this statement and I quote:
Slim build
Finally, we’ve added something new to this release. Sometimes you
don’t need ajax, or you prefer to use one of the many standalone
libraries that focus on ajax requests. And often it is simpler to use
a combination of CSS and class manipulation for all your web
animations. Along with the regular version of jQuery that includes the
ajax and effects modules, we’re releasing a “slim” version that
excludes these modules. All in all, it excludes ajax, effects, and
currently deprecated code.