We're going to look at all the elements with a class of cat, and then test for a class, remove a class, and add a class.
Everything you need to do with a class. Pretty much.
for(const cat of $(".cat")) {
if (cat.classList.contains('fleas')) {
// The cat has the fleas class... remove it
this.classList.remove('fleas');
this.classList.add('clean');
}
}
(I just noticed that this example uses a little helper function I keep handy...
function $(selector) {
return document.querySelectorAll(selector);
}
...and similarly I use:
function $id(id) {
return document.getElementById(id);
}
...)