MutationObserver can be used to observe mutations to the tree of nodes. It’s designed as a replacement for Mutation Events defined in the DOM3 Events specification.

API

var observer = new MutationObserver(callback);
observer.observe(target, options);  // Observe the desired node
observer.disconnect();              // Stop observing
observer.takeRecords();             // Empty and return the record queue

## Example: Random Image Loader
javascript
var matrix = document.querySelector("#imgs");
var imgServ = [
  "http://lorempizza.com/i/380/240",
  "http://lorempixel.com/380/240/"
];

var observer = new MutationObserver(function(mutations) {
  mutations.forEach(function(mutation) {
    var size = matrix.childElementCount;
    matrix.children[size - 1].src = 
      imgServ[Math.floor(imgServ.length * Math.random())] + 
      "#" + Math.random().toString(36).substring(7);
  });
});

observer.observe(matrix, { childList: true });

setInterval(function() {
  matrix.appendChild(document.createElement('img'));
}, 1000);

Don’t miss the spec!