code: function createElementNS(name, namespaceURI) {
      return !namespaceURI || namespaceURI === NS_XHTML ?
          doc.createElement(name) :
          doc.createElementNS(namespaceURI, name);
  }
docs: Create an element, optionally with a known namespace URI.
  
  @param {string} name the element name, e.g. 'div' or 'svg'
  @param {string} [namespaceURI] the element's namespace URI, i.e. the value of
  its `xmlns` attribute or its inferred namespace.
  
  @return {Element}