How to change the cursor on hover in openlayers 3?

It can be done as well without jQuery:

map.on("pointermove", function (evt) {
    var hit = this.forEachFeatureAtPixel(evt.pixel, function(feature, layer) {
        return true;
    }); 
    if (hit) {
        this.getTargetElement().style.cursor = 'pointer';
    } else {
        this.getTargetElement().style.cursor = '';
    }
});

Here is another way to do it:

map.on('pointermove', function(e){
  var pixel = map.getEventPixel(e.originalEvent);
  var hit = map.hasFeatureAtPixel(pixel);
  map.getViewport().style.cursor = hit ? 'pointer' : '';
});