code: function sortedColumnClasses(classes) {
          // extract column classes
          var colClasses = [];
          while (true) {
              var match = COL_REGEX.exec(classes);
              if (!match) {
                  break;
              }
              var colClass = match[0];
              colClasses.push(colClass);
              classes = withoutClass(classes, colClass);
          }
  
          colClasses.sort(compareColumnClasses);
          return classes + ' ' + colClasses.join(' ');
      }
docs: Moves any grid column classes to the end of the class string and sorts the grid classes by ascending screen size.
  @param {string} classes The "class" attribute of a DOM node
  @returns {string} The processed "class" attribute value