This example uses OpenLayers v10.9.0. The latest is v.
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#### Rectangle

simple 7 geometry 4 rectangle 3 box 5 bbox 5 polygon 3

#####

Renders a rectangle on a map.

A simple map with an OSM basemap and a rectangular polygon feature (e.g. a bounding box).

##### main.js

    import Feature from 'ol/Feature.js';
    import Map from 'ol/Map.js';
    import View from 'ol/View.js';
    import {fromExtent} from 'ol/geom/Polygon.js';
    import TileLayer from 'ol/layer/Tile.js';
    import VectorLayer from 'ol/layer/Vector.js';
    import OSM from 'ol/source/OSM.js';
    import VectorSource from 'ol/source/Vector.js';

    const map = new Map({
      layers: [
        new TileLayer({
          source: new OSM(),
        }),
        new VectorLayer({
          source: new VectorSource({
            features: [
              new Feature(
                // Here a `Geometry` is expected, e.g. a `Polygon`, which has a handy function to create a rectangle from bbox coordinates
                fromExtent([-1000000, 5000000, 3000000, 7000000]), // minX, minY, maxX, maxY
              ),
            ],
          }),
        }),
      ],
      target: 'map',
      view: new View({
        center: [1000000, 6000000],
        zoom: 4,
      }),
    });

##### index.html

    <!DOCTYPE html>
    <html lang="en">
      <head>
        <meta charset="UTF-8">
        <title>Rectangle</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>

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

##### package.json

    {
      "name": "rectangle",
      "dependencies": {
        "ol": "10.9.0"
      },
      "devDependencies": {
        "vite": "^3.2.3"
      },
      "scripts": {
        "start": "vite",
        "build": "vite build"
      }
    }