The MutationObserver interface provides the ability to watch for changes being made to the DOM tree. It is designed as a replacement for the older Mutation Events feature which was part of the DOM3 Events specification.

Constructor

MutationObserver()
Creates and returns a new MutationObserver which will invoke a specified callback function when DOM changes occur.

Methods

disconnect()
Stops the MutationObserver instance from receiving further notifications until and unless observe() is called again.
observe()
Configures the MutationObserver to begin receiving notifications through its callback function when DOM changes matching the given options occur.
takeRecords()
Removes all pending notifications from the MutationObserver's notification queue and returns them in a new Array of MutationRecord objects.

Example

The following example was adapted from this blog post.

// Select the node that will be observed for mutations
var targetNode = document.getElementById('some-id');

// Options for the observer (which mutations to observe)
var config = { attributes: true, childList: true, subtree: true };

// Callback function to execute when mutations are observed
var callback = function(mutationsList) {
    for(var 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
var observer = new MutationObserver(callback);

// Start observing the target node for configured mutations
observer.observe(targetNode, config);

// Later, you can stop observing
observer.disconnect();

See also

Specifications

Specification Status Comment
DOM
The definition of 'MutationObserver' in that specification.
Living Standard  

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support

26

18 — 26 Webkit

Yes141115

7

6 — 7 Webkit

MutationObserver() constructor

26

18 — 26 Webkit

Yes141115

7

6 — 7 Webkit

observe18 Yes1411156
disconnect18 Yes1411156
takeRecords18 Yes1411156
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support

26

18 — 26 Webkit

26

18 — 26 Webkit

Yes1414

7

6 — 7 Webkit

Yes
MutationObserver() constructor

26

18 — 26 Webkit

26

18 — 26 Webkit

Yes1414

7

6 — 7 Webkit

Yes
observe1818 Yes14146 Yes
disconnect1818 Yes14146 Yes
takeRecords1818 Yes14146 Yes