Setting up single-player tests before adding spinner

Yes, like that.

The condition of the if statement is where classList.contains is used. to check that “video” is not there in the class list.

In this situation there are a few different ways to handle things.

You could check that the result is false:

if (video.classList.contains("video") === false) {

Or you could check that it’s not true:

if (video.classList.contains("video") !== true) {

Or you could invert the whole result by placing an exclamation mark at the start of things:

if (!video.classList.contains("video") === true) {

And because conditions of if statements are true when their condition is true, you can leave off the === true part.

if (!video.classList.contains("video")) {

Because that condition can be tricky to understand at first glance, it is also preferred to use a well-named variable to make things easier.

That way we could do:

const hasVideo = video.classList.contains("video");
if (hasVideo === false) {

or inverting the === operator:

const hasVideo = video.classList.contains("video");
if (hasVideo !== true) {

or inverting hasVideo:

const hasVideo = video.classList.contains("video");
if (!hasVideo === true) {

or inverting hasVideo without the === operator:

const hasVideo = video.classList.contains("video");
if (!hasVideo) {

All of those work, and they all have different subtleties about what they convey. In this case I prefer the last one. but you can use any one of those you pick.