Layer Z-Index

Square layer Z-index
Triangle layer Z-index

Example of ordering layers using Z-index.

There are are two managed layers (square and triangle) and one unmanaged layer (star).
The Z-index determines the rendering order; with {square: 1, triangle: 0, star: unmanaged} indices, the rendering order is triangle, square and star on top.

main.js

import Feature from 'ol/Feature.js';
import Map from 'ol/Map.js';
import Point from 'ol/geom/Point.js';
import VectorLayer from 'ol/layer/Vector.js';
import VectorSource from 'ol/source/Vector.js';
import View from 'ol/View.js';

const styles = {
  square: {
    'shape-points': 4,
    'shape-radius': 80,
    'shape-angle': Math.PI / 4,
    'shape-stroke-color': 'black',
    'shape-stroke-width': 1,
    'shape-fill-color': 'blue',
  },
  triangle: {
    'shape-points': 3,
    'shape-radius': 80,
    'shape-rotation': Math.PI / 4,
    'shape-stroke-color': 'black',
    'shape-stroke-width': 1,
    'shape-fill-color': 'red',
  },
  star: {
    'shape-points': 5,
    'shape-radius': 80,
    'shape-radius2': 40,
    'shape-rotation': Math.PI / 4,
    'shape-stroke-color': 'black',
    'shape-stroke-width': 1,
    'shape-fill-color': 'green',
  },
};

function createLayer(coordinates, style, zIndex) {
  const feature = new Feature(new Point(coordinates));

  const source = new VectorSource({
    features: [feature],
  });

  const vectorLayer = new VectorLayer({
    source: source,
    style,
  });
  vectorLayer.setZIndex(zIndex);

  return vectorLayer;
}

const layer0 = createLayer([40, 40], styles.star);
const layer1 = createLayer([0, 0], styles.square, 1);
const layer2 = createLayer([0, 40], styles.triangle, 0);

const layers = [];
layers.push(layer1);
layers.push(layer2);

const map = new Map({
  layers: layers,
  target: 'map',
  view: new View({
    center: [0, 0],
    zoom: 18,
  }),
});

layer0.setMap(map);

function bindInputs(id, layer) {
  const idxInput = document.getElementById('idx' + id);
  idxInput.onchange = function () {
    layer.setZIndex(parseInt(this.value, 10) || 0);
  };
  idxInput.value = String(layer.getZIndex());
}
bindInputs(1, layer1);
bindInputs(2, layer2);

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Layer Z-Index</title>
    <link rel="stylesheet" href="node_modules/ol/ol.css">
    <style>
      .map {
        width: 100%;
        height: 400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <div>
      <label for="idx1">
        <input type="number" id="idx1"></input>
        Square layer Z-index
      </label></br>

      <label for="idx2">
        <input type="number" id="idx2"></input>
        Triangle layer Z-index
      </label>
    </div>

    <script type="module" src="main.js"></script>
  </body>
</html>

package.json

{
  "name": "layer-z-index",
  "dependencies": {
    "ol": "9.1.0"
  },
  "devDependencies": {
    "vite": "^3.2.3"
  },
  "scripts": {
    "start": "vite",
    "build": "vite build"
  }
}