i am getting the following error

Parse error: Unexpected token operator «=», expected punc «,» Line
159, column 26

This is my code

  function fitBounds(type=all, shape=null) {

    var bounds = new google.maps.LatLngBounds();



    if ( type == all ){

      if ((circles.length > 0) | (polygons.length > 0)){

        $.each(circles, function(index, circle){

          bounds.union(circle.getBounds());

        });

        $.each(polygons, function(index, polygon){

          polygon.getPath().getArray().forEach(function(latLng){

            bounds.extend(latLng);

          });

        });

      }

    }

    else if ( (type == single) && (shape != null) ) {

      if (shape.type == google.maps.drawing.OverlayType.MARKER) {

        marker_index = markers.indexOf(shape);

        bounds.union(circles[marker_index].getBounds());

      }

      else {

        shape.getPath().getArray().forEach(function(latLng){

          bounds.extend(latLng);

        });

      }

    }



    if (bounds.isEmpty() != true)

    {

      map.fitBounds(bounds);

    }

  }