OpenLayers clear path on marker movement

If you want to achieve desired effect of clearing the route behind the moving marker in mentioned example, all you have to do is to modify moveFeature function, so that at each marker move new route geometry is created that contains only points not covered yet by the moving marker.

Code could then look something like this (just three lines inserted):

var moveFeature = function (event) {
  var vectorContext = ol.render.getVectorContext(event);
  var frameState = event.frameState;

  if (animating) {
    var elapsedTime = frameState.time - now;
    var index = Math.round((speed * elapsedTime) / 1000);

    if (index >= routeLength) {
      stopAnimation(true);
      return;
    }

    var currentPoint = new ol.geom.Point(routeCoords[index]);
    var feature = new ol.Feature(currentPoint);
    vectorContext.drawFeature(feature, styles.geoMarker);

    // three new lines
    var remainingRouteCoords = routeCoords.slice(index);
    var remainingRouteGeom = new ol.geom.LineString(remainingRouteCoords);
    routeFeature.setGeometry(remainingRouteGeom);
  }
  map.render();
};