Why is the DOMSubtreeModified event deprecated in DOM level 3?

Why is the DOMSubtreeModified event deprecated and what are we supposed to use instead?

If you http://www.w3.org/TR/DOM-Level-3-Events/#events-mutationevents">scroll down a bit, you see:

> Warning! The MutationEvent interface was introduced in DOM Level 2 > Events, but has not yet been completely and interoperably implemented > across user agents. In addition, there have been critiques that the > interface, as designed, introduces a performance and implementation > challenge. A new specification is under development with the aim of > addressing the use cases that mutation events solves, but in more > performant manner. Thus, this specification describes mutation events > for reference and completeness of legacy behavior, but deprecates the > use of both the MutationEvent interface and the MutationNameEvent > interface.

The replacement API is mutation observers, which are fully specified in the DOM Living Standard that supercedes all of the DOM level X silliness.

I think the replacement will be mutation observers: https://developer.mozilla.org/en-US/docs/Web/API/MutationObserver

var whatToObserve = {childList: true, attributes: true, subtree: true, attributeOldValue: true, attributeFilter: ['class', 'style']};
var mutationObserver = new MutationObserver(function(mutationRecords) {
  $.each(mutationRecords, function(index, mutationRecord) {
    if (mutationRecord.type === 'childList') {
      if (mutationRecord.addedNodes.length > 0) {
        //DOM node added, do something
      }
      else if (mutationRecord.removedNodes.length > 0) {
        //DOM node removed, do something
      }
    }
    else if (mutationRecord.type === 'attributes') {
      if (mutationRecord.attributeName === 'class') {
        //class changed, do something
      }
    }
  });
});
mutationObserver.observe(document.body, whatToObserve);