Add button functionality within a DOM in leaflet

I can’t seem to figure this one out and I’m assuming that this is a problem of code intendation? I have a button that on click in Leaflet should change the basemap layer.

// Basemap Button - Left panel

L.Control.Watermark = L.Control.extend({
  onAdd: function(map) {
      var Basemap = L.DomUtil.create('img');

      Basemap.src = 'basemap.png';
      Basemap.style.width = '65px';
      Basemap.style.top = '-90px';
      Basemap.style.left = '10px';

      Basemap.addEventListener('click', function() {
        // Change the basemap layer of the map to the OpenStreetMap Street View layer
        var osmStreetViewLayer = L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
          attribution: 'Map data &copy; <a href="https://www.openstreetmap.org/">OpenStreetMap</a> contributors'});

      return Basemap;
  },
});

L.control.watermark({ position: 'topleft' }).addTo(map);

The issue seems to be on closing “});” ?

Returns error on });