<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="https://openlayers.org/en/v5.3.0/css/ol.css" />
  <script type="text/javascript" src="https://openlayers.org/en/v5.3.0/build/ol.js"></script>
  <title>Document</title>
</head>
<body>
  <div id="menu">
      <label>几何图形类型：&nbsp;</label>
      <select id="type">
          <option value="None">无</option>
          <option value="Point">点</option>
          <option value="LineString">线</option>
          <option value="Polygon">多边形</option>
          <option value="Circle">圆</option>
          <option value="Square">正方形</option>
      </select>
  </div>
  <div id="map"></div>

  <script>
      var map = new ol.Map({
          target: 'map',
          layers: [
              new ol.layer.Tile({
                  source: new ol.source.OSM()
              })
          ],
          view: new ol.View({
              center: [ 91.1, 30.41],
              zoom: 4
          })
      });

      var typeSelect = document.getElementById('type');       //绘制类型选择对象
      var draw;                          //ol.Interaction.Draw类的对象

      //实例化一个矢量图层Vector作为绘制层
      var source = new ol.source.Vector();
      var vectorLayer = new ol.layer.Vector({
          source: source,
          style: new ol.style.Style({
              fill: new ol.style.Fill({               //填充样式
                  color: 'rgba(255, 255, 255, 0.2'
              }),
              stroke: new ol.style.Stroke({           //线样式
                  color: '#00c033',
                   2
              }),
              image: new ol.style.Circle({            //点样式
                  radius: 7, 
                  fill: new ol.style.Fill({
                      color: '#00c033'
                  })
              })
          })
      });
      //将绘制层添加到地图容器中
      map.addLayer(vectorLayer);           

      //用户更改绘制类型触发的事件
      typeSelect.onchange = function(e){
          map.removeInteraction(draw);        //移除绘制图形控件
          addInteraction();                   //添加绘制图形控件
      };

      function addInteraction(){
          var typeValue = typeSelect.value;       //绘制类型
          
          if(typeValue !== 'None'){
              var geometryFunction, maxPoints;
              if(typeValue === 'Square'){                 //正方形
                  typeValue = 'Circle';               //设置绘制类型为Circle
                  //设置几何信息变更函数，即创建正方形
                  geometryFunction = ol.interaction.Draw.createRegularPolygon(4);
              }
              console.log(typeValue);
              //实例化图形绘制控件对象并添加到地图容器中
              draw = new ol.interaction.Draw({
                  source: source,
                  type: typeValue,                                //几何图形类型
                  geometryFunction: geometryFunction,             //几何信息变更时的回调函数
                  maxPoints: maxPoints                            //最大点数
              });
              map.addInteraction(draw);
          }else{
              //清空绘制的图形
              source.clear();
          }
      }
  </script>
</body>
</html>

效果图：
openlayers 添加点线面 Demo（可直接运行）-风君雪科技博客