Javascript Anime Support Switch Statement for .animate() Api

Like I mentioned in my answer to your post Check browser compatibility for RequestAnimationFrame and Vanilla JavaScript .animate() API, many ecmascript-6 features like arrow functions and the let and const keywords are used, which cause errors in some browsers the code aims to target - e.g. IE 10 and older. So instead of an arrow function in the callback to setTimeout() use a regular function expression or the name of a function declared with a function declaration, and instead of the const and let keywords, use var.

const LoadRing = document.querySelector(".loader");

Is there only one element with that class name? If so, it would likely be more appropriate to use an id selector instead of a class name to select it.

switch(rafSupport ? true : false){

rafSupport is a boolean (see snippet below for proof) and thus there is no need to use the ternary expression here

let rafSupport = (window.requestAnimationFrame !== undefined);
console.log('typeof rafSupport: ',typeof rafSupport )

The whole switch statement seems like overkill for a boolean condition - most developers would stick to if/else statements.

default:    // Default to Css Fallback.
            var AnimeStyle = document.createElement("link");    // Default Classes to be added back in.
                AnimeStyle.setAttribute("rel", "stylesheet");
                AnimeStyle.setAttribute("type", "text/css");
                AnimeStyle.setAttribute("href", "FallBack.css");
                document.getElementsByTagName("head")[7].appendChild(AnimeStyle);
                return false;

This section of the switch statement is unreachable because:

• the previous cases are true and false, and
• the previous cases both contain break at the end

And are there really 8+ elements with the tag name head??

default:
      return false;
                 // Default to Css Fallback. ie ``Add Back in the Classes`` That governed the original Animation.

This leads to an error:

'return' statement outside of function

Sᴀᴍ Onᴇᴌᴀ has already pointed out several major issues in your code. Besides those, your code also includes unused variables (e.g. cssFallback) and hard-to-read back and forth control flow (since, for some reason, you've decided to stick the animeFallBack function between the definition of webAnimSupport and the switch statement that uses it and possibly calls the function). Your code also has several likely bugs, as pointed out by Sᴀᴍ Onᴇᴌᴀ, and it's not even a complete, testable program (which means that there might well be more bugs that we can't easily spot). In fact, it's doubtful whether your code even qualifies as "working as intended", as required by the Code Review SE topic guidelines.

Based on what you've written in your question, it also looks like you probably don't really understand how basic JavaScript syntax features like if and switch statements actually work. Meanwhile, you've listed a whole bunch of "related articles" in your question, all of which appear to be dealing with considerably more advanced topics than basic JavaScript syntax, and which are probably taking a working knowledge of such syntax for granted.

To be brutally honest, it looks like you've jumped into the deep end of the pool before you've learned how to swim, and that you're now basically just copy-pasting and mixing up random bits of code that you've found online together without actually understanding them, and hoping that they'll somehow magically work.

So my suggestion for you would be to start by finding a good and comprehensive JavaScript tutorial for beginners — I'd personally recommend a printed book, as they're more likely to come as a complete and self-contained package, although there are some fairly decent online tutorials around, too — and reading through it. Since you say you're interested in maintaining compatibility with older browsers, an old pre-ES6 tutorial would suit you fine, although a modern tutorial that covers both styles would be OK too.

You can find plenty of Javascript tutorials — both printed books and online — via Google. I'm not going to even try to provide any specific recommendations, although the first result I got (javascript.info) at least looks fairly decent at a glance (and seems to cover both pre-ES6 and modern syntax, although with an emphasis mostly on the latter).

Once you've picked up a better grasp of the basics, you should be able to come back and apply the suggestions from the references you've listed in your question to come up with a clean and working solution. FWIW, it'll probably end up looking a lot like the code in Adam Taylor's answer to your earlier question.