code: function createDom(id, painter, dpr) {
      var newDom = util.createCanvas();
      var width = painter.getWidth();
      var height = painter.getHeight();
  
      var newDomStyle = newDom.style;
      if (newDomStyle) {  // In node or some other non-browser environment
          newDomStyle.position = 'absolute';
          newDomStyle.left = 0;
          newDomStyle.top = 0;
          newDomStyle.width = width + 'px';
          newDomStyle.height = height + 'px';
  
          newDom.setAttribute('data-zr-dom-id', id);
      }
  
      newDom.width = width * dpr;
      newDom.height = height * dpr;
  
      return newDom;
  }
docs: 创建dom
  
  @inner
  @param {string} id dom id 待用
  @param {Painter} painter painter instance
  @param {number} number