Layer's ZIndex in OpenLayers

zindex.js

let map = new ol.Map({
  target: map_div,
  layers: [
    new ol.layer.Tile({
      source: new ol.source.OSM()
    })
  ],
  view: new ol.View({
    center: ol.proj.fromLonLat(center),
    zoom: zoom
  })
});

let layer_1 = new ol.layer.Vector({
  title: "Point",      
  source: new ol.source.Vector({
    projection:map.getView().projection
  })
});

let layer_2 = new ol.layer.Vector({
  title: "Line",      
  source: new ol.source.Vector({
    projection:map.getView().projection
  })
});

let layer_3 = new ol.layer.Vector({
  title: "Polygon",      
  source: new ol.source.Vector({
    projection:map.getView().projection
  })
});
map.addLayer([layer_1, layer_3, layer_3])

layer_3.setZIndex(1)
layer_2.setZIndex(2)
layer_1.setZIndex(3)