Used to identify a secondary node related to a mutation event. For example, if a mutation event is dispatched to a node indicating that its parent has changed, the relatedNode is the changed parent. If an event is instead dispatched to a subtree indicating a node was changed within it, the relatedNode is the changed node. In the case of the DOMAttrModified event it indicates the Attr node which was modified, added, or removed.
If an event is cancelable, the preventDefault method is used to signify that the event is to be canceled, meaning any default action normally taken by the implementation as a result of the event will not occur.
The stopPropagation method is used prevent further propagation of an event during event flow. The event will complete dispatch to all listeners on the current EventTarget before event flow stops. This method may be used during any stage of event flow.