nl_tokens: Add a CSS class name to an element
pl_tokens: function addClass ( element , classToAdd ) { if ( element . classList ) { <mask> . classList . add ( classToAdd ) ; // Don't need to `throwIfWhitespace` here because `hasElClass` will do it // in the case of classList not being supported. } else if ( ! hasClass ( element , classToAdd ) ) { element . className = ( element . className + ' ' + classToAdd ) . trim ( ) ; } return element ; }