<div id="map">
</div>

#map{
  width:100%;
  height:100vh;
}

var layer = new ol.layer.Tile({
        source: new ol.source.OSM()
      });
      var london = ol.proj.transform([-0.12755, 51.507222], 'EPSG:4326', 'EPSG:3857');
      var view = new ol.View({
        center: london,
        zoom: 6
      });
      // the renderer property can be set to 'canvas', 'dom' or 'webgl'
      var map = new ol.Map({
        renderer: 'webgl',
        target: 'map',
        layers: [layer],
        controls: ol.control.defaults({
          zoom: true,
          attribution: true,
          rotate: false
        }),
        view: view
      });