MutationRecord: attributeName property

The MutationRecord read-only property attributeName contains the name of a changed attribute belonging to a node that is observed by a MutationObserver.

Value

If the record's type is attributes, this is a string representing the name of the mutated attribute of the mutation target.

If the record's type is not attributes, this is null.

In the following example, there are four buttons: two change the style attribute of the h1 element, and two change the class attribute of the h1 element. The script uses a MutationObserver to detect the changes and will update the text below to the name of the last attribute that was changed.

HTML

html

<h1 class="blue" style="color:black;" id="hiMom">Hi, Mom!</h1>

<button id="redButton">Set class to "red"</button>
<button id="blueButton">Set class to "blue"</button>
<button id="whiteButton">Set style to "color:white;"</button>
<button id="blackButton">Set style to "color:black;"</button>

<p id="log">Updated attribute name:</p>

CSS

css

.red {
  background-color: red;
}

.blue {
  background-color: blue;
}

JavaScript

const hiMom = document.querySelector("#hiMom");
const redButton = document.querySelector("#redButton");
const blueButton = document.querySelector("#blueButton ");
const whiteButton = document.querySelector("#whiteButton");
const blackButton = document.querySelector("#blackButton");
const log = document.querySelector("#log");

redButton.addEventListener("click", () => {
  hiMom.classList.add("red");
  hiMom.classList.remove("blue");
});

blueButton.addEventListener("click", () => {
  hiMom.classList.add("blue");
  hiMom.classList.remove("red");
});

whiteButton.addEventListener("click", () => {
  hiMom.style.color = "white";
});

blackButton.addEventListener("click", () => {
  hiMom.style.color = "black";
});

function logLastAttr(mutationRecordArray) {
  for (const record of mutationRecordArray) {
    if (record.type === "attributes") {
      log.textContent = `Updated attribute name: ${record.attributeName}`;
    }
  }
}

const observer = new MutationObserver(logLastAttr);
observer.observe(hiMom, { attributes: true });

Result

Specifications

Specification
DOM Standard # ref-for-dom-mutationrecord-attributename②

Browser compatibility

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