Element: hasAttributeNS() method

The hasAttributeNS() method of the Element interface returns a boolean value indicating whether the current element has the specified attribute with the specified namespace.

If you are working with HTML documents and you don't need to specify the requested attribute as being part of a specific namespace, use the hasAttribute() method instead.

hasAttributeNS(namespace,localName)

// Check that the attribute exists before you set a value
const d = document.getElementById("div1");
if (
  d.hasAttributeNS("http://www.mozilla.org/ns/specialspace/", "special-align")
) {
  d.setAttribute("align", "center");
}