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Attr: localName property

The read-only localName property of the Attr interface returns the local part of the qualified name of an attribute, that is the name of the attribute, stripped from any namespace in front of it. For example, if the qualified name is xml:lang, the returned local name is lang, if the element supports that namespace.

The local name is always in lower case, whatever case at the attribute creation.

Note: HTML only supports a fixed set of namespaces on SVG and MathML elements. These are xml (for the xml:lang attribute), xlink (for the xlink:href, xlink:show, xlink:target and xlink:title attributes) and xpath.

That means that the local name of an attribute of an HTML element is always be equal to its qualified name: Colons are treated as regular characters. In XML, like in SVG or MathML, the colon denotes the end of the prefix and what is before is the namespace; the local name may be different from the qualified name.

Value

A string representing the local part of the attribute's qualified name.

Example

The following example displays the local name of the first attribute of the two first elements, when we click on the appropriate button. The <svg> element is XML and supports namespaces leading to the local name (lang) to be different from the qualified name xml:lang. The <label> element is HTML, that doesn't support namespaces, leading to a local name and the qualified name to be both xml:lang.

HTML

html

<svg xml:lang="en-US" class="struct" height="1" width="1">Click me</svg>
<label xml:lang="en-US" class="struct"></label>

<p>
  <button>Show value for &lt;svg&gt;</button>
  <button>Show value for &lt;label&gt;</button>
</p>

<p>
  Local part of the attribute <code>xml:lang</code>:
  <output id="result">None.</output>
</p>

JavaScript

const elements = document.querySelectorAll(".struct");
const buttons = document.querySelectorAll("button");
const outputEl = document.querySelector("#result");

let i = 0;
for (const button of buttons) {
  const element = elements[i];
  button.addEventListener("click", () => {
    const attribute = element.attributes[0];
    outputEl.value = attribute.localName;
  });
  i++;
}

Specifications

Specification
DOM Standard # dom-attr-localname

Browser compatibility