Which is quite funny as it serves as very good demonstration why one should use jQuery: most of presented examples are 10 times more longer when it comes to code amount or alternatively there is some weird oneliner. All of that for saving 30KB of battle tested cross browser code.

Though note that it doesn't demo anything that only works in IE11+. It doesn't even demo window.fetch().

It's a pretty poor reference for most people. For example, you have no reason to be defaulting to XMLHttpRequest for http requests.