Node.lookupPrefix()

The lookupPrefix() method of the Node interface returns a string containing the prefix for a given namespace URI, if present, and null if not. When multiple prefixes are possible, the first prefix is returned.

Syntax

lookupPrefix(namespace)

Parameters

namespace

A string containing the namespace to look the prefix up.

Note: This parameter is not optional but can be set to null.

Return value

A string containing the corresponding prefix, or null if none has been found. If namespace is null, or the empty string, lookupPrefix() returns null.

If the node is a DocumentType or a DocumentFragment, lookupPrefix() always returns null.

Example

Prefix for <code>http://www.w3.org/2000/svg</code> on &lt;output&gt;:
<output>Not tested</output>.<br />
Prefix for <code>http://www.w3.org/XML/1998/namespace</code> on &lt;output&gt;:
<output>Not tested</output>.<br />
Prefix for <code>http://www.w3.org/TR/html4/</code> on &lt;output&gt;:
<output>Not tested</output>.<br />
Prefix for <code>https://www.w3.org/1999/xlink</code> on &lt;output&gt;:
<output>Not tested</output>.<br />
Prefix for <code>http://www.w3.org/2000/svg</code> on &lt;svg&gt;:
<output>Not tested</output>.<br />
Prefix for <code>https://www.w3.org/1999/xlink</code> on &lt;svg&gt;:
<output>Not tested</output>.<br />
Prefix for <code>http://www.w3.org/XML/1998/namespace</code> on &lt;svg&gt;:
<output>Not tested</output>.<br />
<svg xmlns:t="http://www.w3.org/2000/svg" height="1"></svg>
<button>Click to see the results</button>
const button = document.querySelector('button');
button.addEventListener("click", () => {
  const aHtmlElt = document.querySelector('output');
  const aSvgElt = document.querySelector('svg');

  const result = document.getElementsByTagName('output');
  result[0].value = aHtmlElt.lookupPrefix("http://www.w3.org/2000/svg"); // true
  result[1].value = aHtmlElt.lookupPrefix("http://www.w3.org/XML/1998/namespace"); // false
  result[2].value = aHtmlElt.lookupPrefix("http://www.w3.org/TR/html4/"); // true
  result[3].value = aHtmlElt.lookupPrefix("https://www.w3.org/1999/xlink"); // false
  result[4].value = aSvgElt.lookupPrefix("http://www.w3.org/2000/svg"); // true
  result[5].value = aSvgElt.lookupPrefix("https://www.w3.org/1999/xlink"); // true
  result[6].value = aSvgElt.lookupPrefix("http://www.w3.org/XML/1998/namespace"); // false
});

Specifications

Specification
DOM Standard
# dom-node-lookupprefix

Browser compatibility

BCD tables only load in the browser

See also