js listen for class change event
const btn = document.querySelector('.btn')
const options = {
attributes: true
}
function callback(mutationList, observer) {
mutationList.forEach(function(mutation) {
if (mutation.type === 'attributes' && mutation.attributeName === 'class') {
// handle class change
}
})
}
const observer = new MutationObserver(callback)
observer.observe(btn, options)