function getClassedToRemove(htmlElement) {
  var cssClasses = htmlElement.className.split(' ');
  var sortSequenceRegExp = new RegExp("^".concat(COLUMN_ORDER_PREFIX, "-[0-9]{1,2}$"));
  return cssClasses.filter(function (cssClass) {
    return sortSequenceRegExp.test(cssClass);
  });
}
Get CSS classes which should be removed from column header.

@param {HTMLElement} htmlElement
@returns {Array} Array of CSS classes.