Node: lookupPrefix() method
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
ThelookupPrefix() method of theNode interfacereturns a string containing the prefix for a given namespace URI, if present,andnull if not.When multiple prefixes are possible, the first prefix is returned.
Syntax
lookupPrefix(namespace)Parameters
namespaceA string containing the namespace to look the prefix up. The empty string is equivalent to
null, both causingnullto be returned.Note:This parameter is not optional but can be set to
null.
Return value
A string containing the corresponding prefix, ornull if none has been found.Ifnamespace is null, or the empty string,lookupPrefix() returnsnull.
If the node is aDocumentType or aDocumentFragment,lookupPrefix() always returnsnull.
Example
Note:This example runs in an HTML document, wherexmlns: attributes are ignored (exceptxmlns:xlink). Firefox sets all elements' namespace URIs tonull, while Chrome and Safari appropriately set HTML, SVG, and MathML elements' default namespace URIs. If you want to conduct more meaningful tests, you can open a standaloneSVG document and execute scripts in its context.
<div> <div>Test HTML element</div> <svg> <text>Test SVG element</text> </svg> <svg xmlns:xlink="http://www.w3.org/1999/xlink"> <text>Test SVG element with xlink</text> </svg> <math>Test MathML element</math></div><table> <thead> <tr> <th><code>namespaceURI</code></th> <th><code><div></code></th> <th><code><svg></code></th> <th><code><svg xmlns:xlink></code></th> <th><code><math></code></th> </tr> </thead> <tbody></tbody></table>.hidden { display: none;}const htmlElt = document.querySelector("div");const svgElt = document.querySelector("svg");const svgEltXLink = document.querySelector("#with-xlink");const mathElt = document.querySelector("math");const tbody = document.querySelector("tbody");for (const uri of [ "http://www.w3.org/2000/xmlns/", "http://www.w3.org/XML/1998/namespace", "http://www.w3.org/1999/xhtml", "http://www.w3.org/2000/svg", "http://www.w3.org/1999/xlink", "http://www.w3.org/1998/Math/MathML", "", null,]) { const row = document.createElement("tr"); tbody.appendChild(row); row.appendChild(document.createElement("td")).textContent = JSON.stringify(uri); for (const el of [htmlElt, svgElt, svgEltXLink, mathElt]) { console.log(el, uri, el.lookupPrefix(uri)); row.appendChild(document.createElement("td")).textContent = String( el.lookupPrefix(uri), ); }}Specifications
| Specification |
|---|
| DOM # dom-node-lookupprefix |