// Select the node that will be observed for mutations

const targetNode = document.getElementById('some-id');

// Options for the observer (which mutations to observe)

const config = { attributes: true, childList: true, subtree: true };

// Callback function to execute when mutations are observed

const callback = function(mutationsList, observer) {

    // Use traditional 'for loops' for IE 11 (goodbye IE11!!!!)

    for(const mutation of mutationsList) {

        if (mutation.type === 'childList') {

            console.log('A child node has been added or removed.');

        }

        else if (mutation.type === 'attributes') {

            console.log('The ' + mutation.attributeName + ' attribute was modified.');

        }

    }

};

// Create an observer instance linked to the callback function

const observer = new MutationObserver(callback);

// Start observing the target node for configured mutations

observer.observe(targetNode, config);

// Later, you can stop observing

observer.disconnect();