Setting Labels on Vector features in OpenLayers 5

Question

I am following this very big example to set labels on the style of the vector but it's confusing.

The labels should be the Plot numbers, of each feature, which come from the JSON file.

Also i have seen this API. How can I get the data and display it?

new ol.style.Text({
  font: '12px Calibri,sans-serif',
  textBaseline: 'bottom',
  fill: new ol.style.Fill({
    color: 'rgba(0,0,0,1)'
  }),
  stroke: new ol.style.Stroke({
    color: 'rgba(255,255,255,1)',
    width: 3
  })
});

---

var style_simple = new ol.style.Style({
  fill: new ol.style.Fill({
    color: 'khaki'
  }),
   stroke: new ol.style.Stroke({
      color: 'blue',
      width: 2,
      opacity:1
    })
});

var vector = new ol.layer.Vector({
    source: new ol.source.Vector({
    url: 'JS/getjson.json',
    format: new ol.format.GeoJSON()
    }),style:style_simple
});

var map = new ol.Map({
  target: 'map',
  layers: [roadlayer,vector],
    controls: ol.control.defaults().extend([new ol.control.ScaleLine()]),
    view: new ol.View({
    center: ol.proj.fromLonLat([33.33386, 35.14710]),
    zoom: 14,
    maxZoom: 19
  })
});

Answer 1

@Dataform's answer is correct but creating a new style object every time the function is called is inefficient and can, with large numbers of features, cause performance issues. It is better to predefine a style and set the text property as required

let style = new ol.style.Style({
    // ...........
    text: new ol.style.Text({
      text: ''
    })
    // ...........
  });

let styleFunction = function (feature, resolution) {
  style.getText().setText(feature.get("fieldname_for_plotnumber"));
  return style;
}

Answer 2

You can pass a function to the style option of the vector layer. The function is called for each feature and must return a style object.

let styleFunction = function (feature, resolution) {
  return new ol.style.Style({
    // ...........
    text: new ol.style.Text({
      text: feature.get("fieldname_for_plotnumber")
    })
    // ...........
  });
}

let vector = new ol.layer.Vector({
  // ...........
  style: styleFunction
})