DynamicMeasure_Overlay.js

/*
Create overlay
*/
class Overlay {
  //Contrctor accepts map object, overlay html element, overlay offset, overlay positioning and overlay class
  constructor(map, element = document.getElementById("popup"), offset = [0, -15], positioning = 'bottom-center',   className = 'ol-tooltip-measure ol-tooltip .ol-tooltip-static') {
    this.map = map;
    this.overlay = new ol.Overlay({
      element: element,
      offset: offset,
      positioning: positioning,
      className: className
    });
    this.overlay.setPosition([0,0]);
    this.overlay.element.style.display = 'block';      
    this.map.addOverlay(this.overlay);    
  }
}