code: function extractChartData ( rootNode ) {
  
          var data = [],
              tables = rootNode.getElementsByTagName( "table" );
  
          for ( var i = 0, tableNode; tableNode = tables[ i ]; i++ ) {
  
              if ( tableNode.getAttribute( "data-chart" ) !== null ) {
  
                  data.push( formatData( tableNode ) );
  
              }
  
          }
  
          return data.length ? data : null;
  
      }
docs: 提取数据