MutationEvent

Deprecated: This feature is no longer recommended. Though some browsers might still support it, it may have already been removed from the relevant web standards, may be in the process of being dropped, or may only be kept for compatibility purposes. Avoid using it, and update existing code if possible; see the compatibility table at the bottom of this page to guide your decision. Be aware that this feature may cease to work at any time.

The MutationEvent interface provides event properties that are specific to modifications to the Document Object Model (DOM) hierarchy and nodes.

Note: Using mutation events is problematic:

  • Their design is flawed.
  • Adding DOM mutation listeners to a document profoundly degrades the performance of further DOM modifications to that document (making them 1.5 - 7 times slower!). Moreover, removing the listeners does not reverse the damage.
  • They have poor cross-browser compatibility: Safari doesn't support DOMAttrModified (see WebKit bug 8191) and Firefox doesn't support mutation name events (like DOMElementNameChanged and DOMAttributeNameChanged).

They have been deprecated in favor of mutation observers. Consider using these instead.

Instance properties

This interface also inherits properties from its parent UIEvent, and indirectly from Event.

MutationEvent.attrChange Read only

Indicates what kind of change triggered the DOMAttrModified event. It can be MODIFICATION (1), ADDITION (2) or REMOVAL (3). It has no meaning for other events and is then set to 0.

MutationEvent.attrName Read only

Indicates the name of the node affected by the DOMAttrModified event. It has no meaning for other events and is then set to the empty string ("").

MutationEvent.newValue Read only

In DOMAttrModified events, contains the new value of the modified Attr node. In DOMCharacterDataModified events, contains the new value of the modified CharacterData node. In all other cases, returns the empty string ("").

MutationEvent.prevValue Read only

In DOMAttrModified events, contains the previous value of the modified Attr node. In DOMCharacterDataModified events, contains previous new value of the modified CharacterData node. In all other cases, returns the empty string ("").

MutationEvent.relatedNode Read only

Indicates the node related to the event, like the changed node inside the subtree for DOMSubtreeModified.

Instance methods

MutationEvent.initMutationEvent()

Constructor method that returns a new MutationEvent configured with the parameters given.

Mutation events list

The following is a list of all mutation events:

  • DOMAttrModified (Not supported by Safari)
  • DOMAttributeNameChanged (Not supported by Firefox)
  • DOMCharacterDataModified
  • DOMElementNameChanged (Not supported by Firefox)
  • DOMNodeInserted
  • DOMNodeInsertedIntoDocument
  • DOMNodeRemoved
  • DOMNodeRemovedFromDocument
  • DOMSubtreeModified

Examples

You can register a listener for mutation events using EventTarget.addEventListener() as follows:

js
element.addEventListener(
  "DOMNodeInserted",
  (event) => {
    // …
  },
  false,
);

Specifications

Specification
UI Events
# interface-mutationevent

Browser compatibility

BCD tables only load in the browser

See also