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MutationObserver

files/en-us/web/api/mutationobserver/index.md

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{{APIRef("DOM WHATWG")}}

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

  • {{domxref("MutationObserver.MutationObserver", "MutationObserver()")}}
    • : Creates and returns a new MutationObserver which will invoke a specified callback function when DOM changes occur.

Instance methods

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

Example

The following example was adapted from this blog post.

js
// Select the node that will be observed for mutations
const 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 observed
const 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 function
const observer = new MutationObserver(callback);

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

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

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also