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

geojson 11 vector 86 openstreetmap 22 label 4

#####

## Points

Text:
MaxReso.:
Align:
Baseline:
Rotation:
Font:
Weight:
Placement:
Max Angle:
Exceed Len:
Size:
Line height:
Offset X:
Offset Y:
Color:
O. Color:
O. Width:

## Lines

Text:
MaxReso.:
Align:
Baseline:
Rotation:
Font:
Weight:
Placement:
Max Angle:
Exceed Len:
Size:
Line height:
Offset X:
Offset Y:
Color:
O. Color:
O. Width:

## Polygons

Text:
MaxReso.:
Align:
Baseline:
Rotation:
Font:
Weight:
Placement:
Max Angle:
Exceed Len:
Size:
Line height:
Offset X:
Offset Y:
Color:
O. Color:
O. Width:

Example of GeoJSON features with labels.

This example showcases a number of options that can be set on text styles. When "Text/Wrap" is chosen (for example for the line features), the label is wrapped by inserting the character `\n`, which will create a multi-line label. The "Open Sans" web font will be loaded on demand, to show dynamic font loading.

##### main.js

    import Map from 'ol/Map.js';
    import View from 'ol/View.js';
    import GeoJSON from 'ol/format/GeoJSON.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';
    import CircleStyle from 'ol/style/Circle.js';
    import Fill from 'ol/style/Fill.js';
    import Stroke from 'ol/style/Stroke.js';
    import Style from 'ol/style/Style.js';
    import Text from 'ol/style/Text.js';

    let openSansAdded = false;

    const myDom = {
      points: {
        text: document.getElementById('points-text'),
        align: document.getElementById('points-align'),
        baseline: document.getElementById('points-baseline'),
        rotation: document.getElementById('points-rotation'),
        font: document.getElementById('points-font'),
        weight: document.getElementById('points-weight'),
        size: document.getElementById('points-size'),
        height: document.getElementById('points-height'),
        offsetX: document.getElementById('points-offset-x'),
        offsetY: document.getElementById('points-offset-y'),
        color: document.getElementById('points-color'),
        outline: document.getElementById('points-outline'),
        outlineWidth: document.getElementById('points-outline-width'),
        maxreso: document.getElementById('points-maxreso'),
      },
      lines: {
        text: document.getElementById('lines-text'),
        align: document.getElementById('lines-align'),
        baseline: document.getElementById('lines-baseline'),
        rotation: document.getElementById('lines-rotation'),
        font: document.getElementById('lines-font'),
        weight: document.getElementById('lines-weight'),
        placement: document.getElementById('lines-placement'),
        maxangle: document.getElementById('lines-maxangle'),
        overflow: document.getElementById('lines-overflow'),
        size: document.getElementById('lines-size'),
        height: document.getElementById('lines-height'),
        offsetX: document.getElementById('lines-offset-x'),
        offsetY: document.getElementById('lines-offset-y'),
        color: document.getElementById('lines-color'),
        outline: document.getElementById('lines-outline'),
        outlineWidth: document.getElementById('lines-outline-width'),
        maxreso: document.getElementById('lines-maxreso'),
      },
      polygons: {
        text: document.getElementById('polygons-text'),
        align: document.getElementById('polygons-align'),
        baseline: document.getElementById('polygons-baseline'),
        rotation: document.getElementById('polygons-rotation'),
        font: document.getElementById('polygons-font'),
        weight: document.getElementById('polygons-weight'),
        placement: document.getElementById('polygons-placement'),
        maxangle: document.getElementById('polygons-maxangle'),
        overflow: document.getElementById('polygons-overflow'),
        size: document.getElementById('polygons-size'),
        height: document.getElementById('polygons-height'),
        offsetX: document.getElementById('polygons-offset-x'),
        offsetY: document.getElementById('polygons-offset-y'),
        color: document.getElementById('polygons-color'),
        outline: document.getElementById('polygons-outline'),
        outlineWidth: document.getElementById('polygons-outline-width'),
        maxreso: document.getElementById('polygons-maxreso'),
      },
    };

    const getText = function (feature, resolution, dom) {
      const type = dom.text.value;
      const maxResolution = dom.maxreso.value;
      let text = feature.get('name');

      if (resolution > maxResolution) {
        text = '';
      } else if (type == 'hide') {
        text = '';
      } else if (type == 'shorten') {
        text = truncate(text, 12);
      } else if (
        type == 'wrap' &&
        (!dom.placement || dom.placement.value != 'line')
      ) {
        text = stringDivider(text, 16, '\n');
      }

      return text;
    };

    const createTextStyle = function (feature, resolution, dom) {
      const align = dom.align.value;
      const baseline = dom.baseline.value;
      const size = dom.size.value;
      const height = dom.height.value;
      const offsetX = parseInt(dom.offsetX.value, 10);
      const offsetY = parseInt(dom.offsetY.value, 10);
      const weight = dom.weight.value;
      const placement = dom.placement ? dom.placement.value : undefined;
      const maxAngle = dom.maxangle ? parseFloat(dom.maxangle.value) : undefined;
      const overflow = dom.overflow ? dom.overflow.value == 'true' : undefined;
      const rotation = parseFloat(dom.rotation.value);
      if (dom.font.value == "'Open Sans'" && !openSansAdded) {
        const openSans = document.createElement('link');
        openSans.href = 'https://fonts.googleapis.com/css?family=Open+Sans';
        openSans.rel = 'stylesheet';
        document.head.appendChild(openSans);
        openSansAdded = true;
      }
      const font = weight + ' ' + size + '/' + height + ' ' + dom.font.value;
      const fillColor = dom.color.value;
      const outlineColor = dom.outline.value;
      const outlineWidth = parseInt(dom.outlineWidth.value, 10);

      return new Text({
        textAlign: align == '' ? undefined : align,
        textBaseline: baseline,
        font: font,
        text: getText(feature, resolution, dom),
        fill: new Fill({color: fillColor}),
        stroke: new Stroke({color: outlineColor, width: outlineWidth}),
        offsetX: offsetX,
        offsetY: offsetY,
        placement: placement,
        maxAngle: maxAngle,
        overflow: overflow,
        rotation: rotation,
      });
    };

    // Polygons
    function polygonStyleFunction(feature, resolution) {
      return new Style({
        stroke: new Stroke({
          color: 'blue',
          width: 1,
        }),
        fill: new Fill({
          color: 'rgba(0, 0, 255, 0.1)',
        }),
        text: createTextStyle(feature, resolution, myDom.polygons),
      });
    }

    const vectorPolygons = new VectorLayer({
      source: new VectorSource({
        url: 'data/geojson/polygon-samples.geojson',
        format: new GeoJSON(),
      }),
      style: polygonStyleFunction,
    });

    // Lines
    function lineStyleFunction(feature, resolution) {
      return new Style({
        stroke: new Stroke({
          color: 'green',
          width: 2,
        }),
        text: createTextStyle(feature, resolution, myDom.lines),
      });
    }

    const vectorLines = new VectorLayer({
      source: new VectorSource({
        url: 'data/geojson/line-samples.geojson',
        format: new GeoJSON(),
      }),
      style: lineStyleFunction,
    });

    // Points
    function pointStyleFunction(feature, resolution) {
      return new Style({
        image: new CircleStyle({
          radius: 10,
          fill: new Fill({color: 'rgba(255, 0, 0, 0.1)'}),
          stroke: new Stroke({color: 'red', width: 1}),
        }),
        text: createTextStyle(feature, resolution, myDom.points),
      });
    }

    const vectorPoints = new VectorLayer({
      source: new VectorSource({
        url: 'data/geojson/point-samples.geojson',
        format: new GeoJSON(),
      }),
      style: pointStyleFunction,
    });

    const map = new Map({
      layers: [
        new TileLayer({
          source: new OSM(),
        }),
        vectorPolygons,
        vectorLines,
        vectorPoints,
      ],
      target: 'map',
      view: new View({
        center: [-8161939, 6095025],
        zoom: 8,
      }),
    });

    document
      .getElementById('refresh-points')
      .addEventListener('click', function () {
        vectorPoints.setStyle(pointStyleFunction);
      });

    document.getElementById('refresh-lines').addEventListener('click', function () {
      vectorLines.setStyle(lineStyleFunction);
    });

    document
      .getElementById('refresh-polygons')
      .addEventListener('click', function () {
        vectorPolygons.setStyle(polygonStyleFunction);
      });

    /**
     * @param {string} string String
     * @param {number} n The max number of characters to keep.
     * @return {string} Truncated string.
     */
    function truncate(string, n) {
      return string.length > n ? string.slice(0, n - 1) + '…' : string.slice();
    }

    // https://stackoverflow.com/questions/14484787/wrap-text-in-javascript
    function stringDivider(str, width, spaceReplacer) {
      if (str.length > width) {
        let p = width;
        while (p > 0 && str[p] != ' ' && str[p] != '-') {
          p--;
        }
        if (p > 0) {
          let left;
          if (str.substring(p, p + 1) == '-') {
            left = str.substring(0, p + 1);
          } else {
            left = str.substring(0, p);
          }
          const right = str.substring(p + 1);
          return left + spaceReplacer + stringDivider(right, width, spaceReplacer);
        }
      }
      return str;
    }

##### index.html

    <!DOCTYPE html>
    <html lang="en">
      <head>
        <meta charset="UTF-8">
        <title>Vector Labels</title>
        <link rel="stylesheet" href="node_modules/ol/ol.css">
        <style>
          .map {
            width: 100%;
            height: 400px;
          }
          .edit-form {
            display: inline-block;
            margin: 5px;
            padding: 10px;
            border: 1px solid black;
            white-space: nowrap;
          }

          .edit-form h2 {
            font-size: 1.5em;
          }

          .edit-form input[type="button"] {
            float: right;
          }

          .edit-form-elem label {
            display: inline-block;
            width: 85px;
          }

          .edit-form-elem input[type="text"],
          .edit-form-elem select {
            width: 130px;
          }
        </style>
      </head>
      <body>
        <div id="map" class="map"></div>

        <div class="edit-form">
          <input id="refresh-points" type="button" value="Refresh" />
          <h2>Points</h2>
          <div class="edit-form-elem">
            <label for="points-text">Text: </label>
            <select id="points-text">
              <option value="hide">Hide</option>
              <option value="normal">Normal</option>
              <option value="shorten" selected="selected">Shorten</option>
              <option value="wrap">Wrap</option>
            </select>
            <br />
            <label for="points-maxreso" title="Max Resolution Denominator">MaxReso.: </label>
            <select id="points-maxreso">
              <option value="38400">38,400</option>
              <option value="19200">19,200</option>
              <option value="9600">9,600</option>
              <option value="4800">4,800</option>
              <option value="2400">2,400</option>
              <option value="1200" selected="selected">1,200</option>
              <option value="600">600</option>
              <option value="300">300</option>
              <option value="150">150</option>
              <option value="75">75</option>
              <option value="32">32</option>
              <option value="16">16</option>
              <option value="8">8</option>
            </select>
            <br />
            <label for="points-align">Align: </label>
            <select id="points-align">
              <option value="center" selected="selected">Center</option>
              <option value="end">End</option>
              <option value="left">Left</option>
              <option value="right">Right</option>
              <option value="start">Start</option>
            </select>
            <br />
            <label for="points-baseline">Baseline: </label>
            <select id="points-baseline">
              <option value="alphabetic">Alphabetic</option>
              <option value="bottom">Bottom</option>
              <option value="hanging">Hanging</option>
              <option value="ideographic">Ideographic</option>
              <option value="middle" selected="selected">Middle</option>
              <option value="top">Top</option>
            </select>
            <br />
            <label for="points-rotation">Rotation: </label>
            <select id="points-rotation">
              <option value="0">0°</option>
              <option value="0.785398164">45°</option>
              <option value="1.570796327">90°</option>
            </select>
            <br />
            <label for="points-font">Font: </label>
            <select id="points-font">
              <option value="Arial" selected="selected">Arial</option>
              <option value="'Courier New'">Courier New</option>
              <option value="'Open Sans'">Open Sans</option>
              <option value="Verdana">Verdana</option>
            </select>
            <br />
            <label for="points-weight">Weight: </label>
            <select id="points-weight">
              <option value="bold">Bold</option>
              <option value="normal" selected="selected">Normal</option>
            </select>
            <br />
            <label for="points-placement">Placement: </label>
            <select disabled id="points-placement">
              <option value="line">Line</option>
              <option value="point" selected="selected">Point</option>
            </select>
            <br />
            <label for="points-maxangle">Max Angle: </label>
            <select disabled id="points-maxangle">
              <option value="0.7853981633974483" selected="selected">45°</option>
              <option value="2.0943951023931953">120°</option>
              <option value="6.283185307179586">360°</option>
            </select>
            <br />
            <label for="points-overflow">Exceed Len: </label>
            <select disabled id="points-overflow">
              <option value="true">True</option>
              <option value="false" selected="selected">False</option>
            </select>
            <br />
            <label for="points-size">Size: </label>
            <input type="text" value="12px" id="points-size" />
            <br />
            <label for="points-height">Line height: </label>
            <input type="text" value="1" id="points-height" />
            <br />
            <label for="points-offset-x">Offset X: </label>
            <input type="text" value="0" id="points-offset-x" />
            <br />
            <label for="points-offset-y">Offset Y: </label>
            <input type="text" value="0" id="points-offset-y" />
            <br />
            <label for="points-color">Color: </label>
            <input type="text" value="#aa3300" id="points-color" />
            <br />
            <label for="points-outline" title="Outline Color">O. Color: </label>
            <input type="text" value="#ffffff" id="points-outline" />
            <br />
            <label for="points-outline-width" title="Outline Width">O. Width: </label>
            <input type="text" value="3" id="points-outline-width" />
          </div>
        </div>

        <div class="edit-form">
          <input id="refresh-lines" type="button" value="Refresh" />
          <h2>Lines</h2>
          <div class="edit-form-elem">
            <label for="lines-text">Text: </label>
            <select id="lines-text">
              <option value="hide">Hide</option>
              <option value="normal">Normal</option>
              <option value="shorten">Shorten</option>
              <option value="wrap" selected="selected">Wrap</option>
            </select>
            <br />
            <label for="lines-maxreso" title="Max Resolution Denominator">MaxReso.: </label>
            <select id="lines-maxreso">
              <option value="38400">38,400</option>
              <option value="19200">19,200</option>
              <option value="9600">9,600</option>
              <option value="4800">4,800</option>
              <option value="2400">2,400</option>
              <option value="1200" selected="selected">1,200</option>
              <option value="600">600</option>
              <option value="300">300</option>
              <option value="150">150</option>
              <option value="75">75</option>
              <option value="32">32</option>
              <option value="16">16</option>
              <option value="8">8</option>
            </select>
            <br />
            <label for="lines-align">Align: </label>
            <select id="lines-align">
              <option value="" selected="selected"></option>
              <option value="center">Center</option>
              <option value="end">End</option>
              <option value="left">Left</option>
              <option value="right">Right</option>
              <option value="start">Start</option>
            </select>
            <br />
            <label for="lines-baseline">Baseline: </label>
            <select id="lines-baseline">
              <option value="alphabetic">Alphabetic</option>
              <option value="bottom">Bottom</option>
              <option value="hanging">Hanging</option>
              <option value="ideographic">Ideographic</option>
              <option value="middle" selected="selected">Middle</option>
              <option value="top">Top</option>
            </select>
            <br />
            <label for="lines-rotation">Rotation: </label>
            <select id="lines-rotation">
              <option value="0">0°</option>
              <option value="0.785398164">45°</option>
              <option value="1.570796327">90°</option>
            </select>
            <br />
            <label for="lines-font">Font: </label>
            <select id="lines-font">
              <option value="Arial">Arial</option>
              <option value="'Courier New'" selected="selected">Courier New</option>
              <option value="'Open Sans'">Open Sans</option>
              <option value="Verdana">Verdana</option>
            </select>
            <br />
            <label for="lines-weight">Weight: </label>
            <select id="lines-weight">
              <option value="bold" selected="selected">Bold</option>
              <option value="normal">Normal</option>
            </select>
            <br />
            <label for="lines-placement">Placement: </label>
            <select id="lines-placement">
              <option value="line">Line</option>
              <option value="point" selected="selected">Point</option>
            </select>
            <br />
            <label for="lines-maxangle">Max Angle: </label>
            <select id="lines-maxangle">
              <option value="0.7853981633974483" selected="selected">45°</option>
              <option value="2.0943951023931953">120°</option>
              <option value="6.283185307179586">360°</option>
            </select>
            <br />
            <label for="lines-overflow">Exceed Len: </label>
            <select id="lines-overflow">
              <option value="true">True</option>
              <option value="false" selected="selected">False</option>
            </select>
            <br />
            <label for="lines-size">Size: </label>
            <input type="text" value="12px" id="lines-size" />
            <br />
            <label for="lines-height">Line height: </label>
            <input type="text" value="1.2" id="lines-height" />
            <br />
            <label for="lines-offset-x">Offset X: </label>
            <input type="text" value="0" id="lines-offset-x" />
            <br />
            <label for="lines-offset-y">Offset Y: </label>
            <input type="text" value="0" id="lines-offset-y" />
            <br />
            <label for="lines-color">Color: </label>
            <input type="text" value="green" id="lines-color" />
            <br />
            <label for="lines-outline" title="Outline Color">O. Color: </label>
            <input type="text" value="#ffffff" id="lines-outline" />
            <br />
            <label for="lines-outline-width" title="Outline Width">O. Width: </label>
            <input type="text" value="3" id="lines-outline-width" />
          </div>
        </div>

        <div class="edit-form">
          <input id="refresh-polygons" type="button" value="Refresh" />
          <h2>Polygons</h2>
          <div class="edit-form-elem">
            <label for="polygons-text">Text: </label>
            <select id="polygons-text">
              <option value="hide">Hide</option>
              <option value="normal" selected="selected">Normal</option>
              <option value="shorten">Shorten</option>
              <option value="wrap">Wrap</option>
            </select>
            <br />
            <label for="polygons-maxreso" title="Max Resolution Denominator">MaxReso.: </label>
            <select id="polygons-maxreso">
              <option value="38400">38,400</option>
              <option value="19200">19,200</option>
              <option value="9600">9,600</option>
              <option value="4800">4,800</option>
              <option value="2400">2,400</option>
              <option value="1200" selected="selected">1,200</option>
              <option value="600">600</option>
              <option value="300">300</option>
              <option value="150">150</option>
              <option value="75">75</option>
              <option value="32">32</option>
              <option value="16">16</option>
              <option value="8">8</option>
            </select>
            <br />
            <label for="polygons-align">Align: </label>
            <select id="polygons-align">
              <option value="" selected="selected"></option>
              <option value="center">Center</option>
              <option value="end">End</option>
              <option value="left">Left</option>
              <option value="right">Right</option>
              <option value="start">Start</option>
            </select>
            <br />
            <label for="polygons-baseline">Baseline: </label>
            <select id="polygons-baseline">
              <option value="alphabetic">Alphabetic</option>
              <option value="bottom">Bottom</option>
              <option value="hanging">Hanging</option>
              <option value="ideographic">Ideographic</option>
              <option value="middle" selected="selected">Middle</option>
              <option value="top">Top</option>
            </select>
            <br />
            <label for="polygons-rotation">Rotation: </label>
            <select id="polygons-rotation">
              <option value="0">0°</option>
              <option value="0.785398164">45°</option>
              <option value="1.570796327">90°</option>
            </select>
            <br />
            <label for="polygons-font">Font: </label>
            <select id="polygons-font">
              <option value="Arial">Arial</option>
              <option value="'Courier New'">Courier New</option>
              <option value="'Open Sans'">Open Sans</option>
              <option value="Verdana" selected="selected">Verdana</option>
            </select>
            <br />
            <label for="polygons-weight">Weight: </label>
            <select id="polygons-weight">
              <option value="bold" selected="selected">Bold</option>
              <option value="normal">Normal</option>
            </select>
            <br />
            <label for="polygons-placement">Placement: </label>
            <select id="polygons-placement">
              <option value="line">Line</option>
              <option value="point" selected="selected">Point</option>
            </select>
            <br />
            <label for="polygons-maxangle">Max Angle: </label>
            <select id="polygons-maxangle">
              <option value="0.7853981633974483" selected="selected">45°</option>
              <option value="2.0943951023931953">120°</option>
              <option value="6.283185307179586">360°</option>
            </select>
            <br />
            <label for="polygons-overflow">Exceed Len: </label>
            <select id="polygons-overflow">
              <option value="true">True</option>
              <option value="false" selected="selected">False</option>
            </select>
            <br />
            <label for="polygons-size">Size: </label>
            <input type="text" value="10px" id="polygons-size" />
            <br />
            <label for="polygons-height">Line height: </label>
            <input type="text" value="1" id="polygons-height" />
            <br />
            <label for="polygons-offset-x">Offset X: </label>
            <input type="text" value="0" id="polygons-offset-x" />
            <br />
            <label for="polygons-offset-y">Offset Y: </label>
            <input type="text" value="0" id="polygons-offset-y" />
            <br />
            <label for="polygons-color">Color: </label>
            <input type="text" value="blue" id="polygons-color" />
            <br />
            <label for="polygons-outline" title="Outline Color">O. Color: </label>
            <input type="text" value="#ffffff" id="polygons-outline" />
            <br />
            <label for="polygons-outline-width" title="Outline Width">O. Width: </label>
            <input type="text" value="3" id="polygons-outline-width" />
          </div>
        </div>

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

##### package.json

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