Hi,
This code bellow gives me the viewer only if i don’t load the modeler module, I couldn’t find a doc about the “BpmnViewer” and its options.
var viewer = new BpmnViewer({ container: '#js-canvas' });
viewer.importXML(diagram, function(err) {
  if (!err) {
    console.log('success!');
    viewer.get('canvas').zoom('fit-viewport');
  } else {
    console.log('something went wrong:', err);
  }
});
Cheers