如何创建一个SVG DOM

/* 创建svg对象 */

var SVG_NS = "http://www.w3.org/2000/svg";
var XLINK_NS = "http://www.w3.org/1999/xlink";

var ATTR_MAP = {
  "className": "class",
  "svgHref": "href"
};

var NS_MAP = {
  "svgHref": XLINK_NS
};

function makeSVG(tag, attributes) {
  var elem = document.createElementNS(SVG_NS, tag);
  for (var attribute in attributes) {
    var name = (attribute in ATTR_MAP ? ATTR_MAP[attribute] : attribute);
    var value = attributes[attribute];
    if (attribute in NS_MAP)
      elem.setAttributeNS(NS_MAP[attribute], name, value);
    else
      elem.setAttribute(name, value);
    }
  return elem;
}