MutationObserver

BaselineWidely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

TheMutationObserver interface provides the ability to watch for changes being made to theDOM tree. It is designed as a replacement for the olderMutation Events feature, which was part of the DOM3 Events specification.

Constructor

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

Instance methods

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

Example

The following example was adapted fromthis blog post.

// Select the node that will be observed for mutationsconst 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 observedconst callback = (mutationList, observer) => {  for (const mutation of mutationList) {    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 functionconst observer = new MutationObserver(callback);// Start observing the target node for configured mutationsobserver.observe(targetNode, config);// Later, you can stop observingobserver.disconnect();