Overview
The following mutation events harm performance and are deprecated in the DOM events spec:
DOMAttrModified
DOMAttributeNameChanged
DOMCharacterDataModified
DOMElementNameChanged
DOMNodeInserted
DOMNodeInsertedIntoDocument
DOMNodeRemoved
DOMNodeRemovedFromDocument
DOMSubtreeModified
Recommendations
Under URLs, Lighthouse reports each mutation event listener that it found
in your code. Replace each of these mutation events with a MutationObserver
.
See MutationObserver
on MDN for more help.
More information
Lighthouse collects all of the event listeners on the page, and flags any listener that uses one of the types listed above.
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