code: function columnTotalWidth(columns, prop) {
      var totalWidth = 0;
      if (columns) {
          for (var _i = 0, columns_1 = columns; _i < columns_1.length; _i++) {
              var c = columns_1[_i];
              var has = prop && c[prop];
              var width = has ? c[prop] : c.width;
              totalWidth = totalWidth + parseFloat(width);
          }
      }
      return totalWidth;
  }
docs: Calculates the total width of all columns and their groups