openlayers3 : center and zoom extent to KML limits

Question

Basic script to display a kml file on a tiled background with openlayer; I just switched from version 2 to 4.65, how can I zoom to the limits of the kml geometry ("vector" here) ?

        var wmsSource = new ol.source.TileWMS({
            url: "https://sedac.ciesin.columbia.edu/geoserver/wms",
            params: {"LAYERS": "other:wwf-terrestrial-biomes", "TILED": true},
            serverType: "geoserver"
          });

        var wmsLayer = new ol.layer.Tile({
            opacity: 0.15,
            visible: true,
            source: wmsSource
          });

        var vector = new ol.layer.Vector({
            source: new ol.source.Vector({
            url: "kml_file.kml",
            format: new ol.format.KML()
        })
    });

        var map = new ol.Map({
            target: "map-canvas",
            layers: [wmsLayer, vector],
            controls: ol.control.defaults().extend([
                new ol.control.ScaleLine({units: "metric"}), 
                new ol.control.FullScreen()
            ]),
            view: new ol.View({
                center: ol.proj.transform([37.41, 8.82], "EPSG:4326", "EPSG:3857"),
                zoom: 3
            })
        });

I'd like to replace the zoom: 3 and have the map centered and extended to the kml limits ?

Note : I used kmllayer.events.register("loadend", kmllayer, function(evt){map.zoomToExtent(kmllayer.getDataExtent())}); with OpenLayers2...

Answer 1

The following should do what you want

var vectorSource = vector.getSource();
vectorSource.once('change', function(e){
    if (vectorSource.getState() === 'ready') {
        var extent = vectorSource.getExtent();
        map.getView().fit(extent);
    }
});

Solution mainly adapted from How to get the extent of a GeoJSON vector source? (changed the variable name & removed second argument in map.getView().fit (required in the old time, now optional, not needed most of the time, like here)