The Node.namespaceURI read-only property returns the namespace URI of the node, or null if the node is not in a namespace. When the node is a document, it returns the XML namespace for the current document.
TheSVGCircleElement interface is an interface for the <circle> element. The circle element is defined by the cx and cy attributes, that denote the coordinates of the centre of the circle. It also has a radius attribute r that denotes the radius of the circle. The radius value must be positive to allow the successful rendering of the element.