Simple MutationObserver to understand the behaviour of DOM modifications for a specific AJAX library.

mutationObserver.js

// Just a method to log NodeList content
var logChildrenModifications = function(type, array) {
    if (array instanceof NodeList) {
        for (var i = 0; i < array.length; i++) {
            if (array.item(i) instanceof NodeList) {
                logChildrenModifications(type, array.item(i));
            } else {
                console.log(type + ' ' + array.item(i).nodeName);
            }
        }
    } else {
        console.log(type + ' ' + array.nodeName);
    }
};

// https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#mutationobserver
var observer = new MutationObserver(function(mutations) {
    mutations.forEach(function(mutation) {
        if (mutation.type === 'childList') {
            if (mutation.removedNodes && mutation.removedNodes.length > 0) {
                logChildrenModifications('removeChild', mutation.removedNodes);
            }
            if (mutation.addedNodes && mutation.addedNodes.length > 0) {
                logChildrenModifications('appendChild', mutation.addedNodes);
            }
            if (mutation.previousSibling && mutation.previousSibling.length > 0) {
                logChildrenModifications('insertBefore', mutation.previousSibling);
            }
            if (mutation.nextSibling && mutation.nextSibling.length > 0) {
                logChildrenModifications('insertAfter', mutation.nextSibling);
            }
        }
        if (mutation.type === 'attributes') {
            console.log('attribute modified : ' + mutation.attributeName);
        }
    });
    console.log('---');
});

// The target to observe
var targetNode = document.getElementById('theIdToTarget');

// https://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#mutationobserverinit
var config = {
    childList: true,
    attributes: true,
    subtree: true
};

// Observe the given node with the given config
observer.observe(targetNode, config);

// To stop the observation !!! Don't forget to disconnect before settign a new observer !
// observer.disconnect();