DynamicMeasure_Draw.js

/*
Create a Draw interaction for LineString and Polygon
*/
class Draw {  
  //Constructor accepts geometry type, map object and vector layer
  constructor(type, map, vector_layer) {
    this.map = map;
    this.vector_layer = vector_layer;
    this.draw = new ol.interaction.Draw({
        type: type,
        stopClick: true
    });
    this.draw.on('drawstart', this.onDrawStart);
    this.draw.on('drawend', this.onDrawEnd);
    this.map.addInteraction(this.draw);        
  } 
}