Openlayers中的投影EPSG：3067不显示OSM

Question

我对Openlayers还是陌生的，并且正忙于投影。我尝试使用投影EPSG：3067创建地图，但是我的代码未显示任何内容。我的代码尝试使用库proj4js定义投影，并在openlayers地图中使用投影。代码没有给出任何错误，并且在openlayers文档中进行了长时间搜索之后，我仍然找不到错误。错误可能在哪里？

<script>
//Defining projection with proj4
proj4.defs('EPSG:3067','+proj=utm +zone=35 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs');
ol.proj.proj4.register(proj4);

//Creating projection to Openlayer
var projection = ol.proj.get('EPSG:3067');

//Defining extent and settingit to projection
var extent = [50199.4814, 6582464.0358, 761274.6247, 7799839.8902];
projection.setExtent(extent);

//Creating map
var map = new ol.Map({
    target: 'map',
    layers: [
        new ol.layer.Tile({
            source: new ol.source.OSM()
        })
    ],
    //Creating view for map
    view: new ol.View({
        projection: projection,
        extent: extent,
        zoom: 4
    })
});

</script>