问无法在OpenLayers3中获得相对URL

EN

<script>

  var vectorSource = new ol.source.GeoJSON({
    projection: 'EPSG:3857',

    //not working relative url:
    //  url: '../assets/data/nutsv9_lea.geojson'

    //working url (with the targetfile in a directory below the directory containing this script) but only working in Firefox and not working in Chrome and InternetExplorer
    url: 'data/nutsv9_lea.geojson'
  });

  var vectorLayer = new ol.layer.Vector({
    source: vectorSource
  });

  var center = ol.proj.transform([5.231819, 52.091852], 'EPSG:4326', 'EPSG:3857');

  var view = new ol.View({
    center: center,
    zoom: 5
  });

  var map = new ol.Map({
    target: 'map',
    layers: [vectorLayer],
    view: view
  });
</script>