Function to listen for attribute changes. Useful for preventing inconsistency between your internal module state and the DOM. (IE11+)

attributeObserver.es6

const attributeObserver = (element, attr, cb) => {

	const mutObserver = new MutationObserver(mutations => {
		mutations.forEach(mut => {
			mut.attributeName === attr && cb(element.getAttribute(attr));
		});
	});

	mutObserver.observe(element, {
		attributes: true,
		attributeFilter: [ attr ]
	});

	return mutObserver;

};

const handleAttrChangeFn = attrValue => console.log(attrValue);
const ariaHiddenObserver = attributeObserver(document.getElementById('foo'), 'aria-hidden', handleAttrChangeFn);

ariaHiddenObserver.disconnect();