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MutationEvent: prevValue property

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 prevValue read-only property of the MutationEvent interface returns a string. In DOMAttrModified events, it represents the previous value of the Attr node. In DOMCharacterDataModified events, it contains the previous value of the CharacterData node. In all other cases, returns the empty string ("").

Value

A string.

Examples

js

element.addEventListener(
  "DOMAttrModified",
  (event) => {
    console.log(event.previousValue);
  },
  false,
);

Specifications

Specification
UI Events
# dom-mutationevent-prevvalue

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Internet Explorer Opera Safari WebView Android Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet
prevValue 1 12 1 9 ≤12.1 1 4.4 18 4 ≤12.1 1 1.0

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https://developer.mozilla.org/en-US/docs/Web/API/MutationEvent/prevValue