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web api instance method

Node: isDefaultNamespace() method

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The isDefaultNamespace() method of the Node interface accepts a namespace URI as an argument. It returns a boolean value that is true if the namespace is the default namespace on the given node and false if not. The default namespace can be retrieved with lookupNamespaceURI() by passing null as the argument.

Syntax

isDefaultNamespace(namespaceURI)

Parameters

  • namespaceURI
    • : A string representing the namespace against which the element will be checked. The empty string is equivalent to null.

      [!NOTE] namespaceURI is not an optional parameter, but can be null.

Return value

A boolean value that holds the return value true or false, indicating if the parameter is the default namespace, or not. It is equivalent to node.lookupNamespaceURI(null) === namespaceURI.

Example

[!NOTE] This example runs in an HTML document, where xmlns: attributes are ignored (except xmlns:xlink). Firefox sets all elements’ namespace URI to null, 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 standalone SVG document and execute scripts in its context.

<div class="hidden">
  <div>Test HTML element</div>
  <svg>
    <text>Test SVG element</text>
  </svg>
  <svg xmlns:xlink="http://www.w3.org/1999/xlink" id="with-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>&lt;div&gt;</code></th>
      <th><code>&lt;svg&gt;</code></th>
      <th><code>&lt;svg xmlns:xlink&gt;</code></th>
      <th><code>&lt;math&gt;</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.isDefaultNamespace(uri));
    row.appendChild(document.createElement("td")).textContent = String(
      el.isDefaultNamespace(uri),
    );
  }
}
Interactive exampleOpen the canonical MDN source to run this embedded demo.

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also