code: function(tagName, attr, range){
      var iframeDOM = this.document
      ,elem = document.createElement(tagName)
      for(var key in attr){
        elem.setAttribute(key, attr[key]);
      }
      elem.removeAttribute('text');
  
      if(iframeDOM.selection){ //IE
        var text = range.text || attr.text;
        if(tagName === 'a' && !text) return;
        if(text){
          elem.innerHTML = text;
        }
        range.pasteHTML($(elem).prop('outerHTML')); 
        range.select();
      } else { //非IE
        var text = range.toString() || attr.text;
        if(tagName === 'a' && !text) return;
        if(text){
          elem.innerHTML = text;
        }
        range.deleteContents();
        range.insertNode(elem);
      }
    }
docs: iframe初始化