code: function createOffsideInstance( el, options, offsideId ) {
  
                  // Check if provided element exists before using it to instantiate an Offside instance
                  var domEl = el !== undefined ?
                      getDomElements( el ) :
                      getDomElements( '.offside' );
  
                  // If provided el exists initialize an Offside instance, else return null
                  return domEl !== false ?
                      new OffsideInstance( domEl[0], options, offsideId ) :
                      null;
              }
docs: Offside constructor wrapper It supplies a wrapper around OffsideInstance constructor to prevent instance initialization when casted on a non-existing DOM element See: http://stackoverflow.com/a/8618792