Javascript Angular 使用复选框在 Leaflet map 上显示删除图层

I'm working on Angular CLI in which I've built a Leaflet Map.
The goal is to select layers with checkboxes to display them in the map as the HTML part is showing :

 <div class="form-check">
 <input class="form-check-input" type="checkbox" (change)="testCheck($event)" name="releves">
 <label class="form-check-label">Layer 1</label>
 </div>

当我 Select "Layer1"时，复选框被选中，这将运行testCheck($event).

在Typescript部分显示时，我添加了几行代码以在 map 上显示图层:

 testCheck(event: any){
      if (event.target.name == 'releves'){
         var releves = L.tileLayer.wms('https://URL_TO_THE_WMS', {layers: 'myLayer',format: 'image/png',transparent:true});
         if (event.target.checked === true){ 
                 if (! this.mymap.hasLayer(releves)) {
                    releves.addTo(this.mymap);
                 }
                 else if (this.mymap.hasLayer(releves)) {
                    // do nothing
                 }
            let i = 0;
            this.mymap.eachLayer(function(){ i += 1; });
            console.log('Map has', i, 'layers.');
         }
         else {
                if (this.mymap.hasLayer(releves)) {
                    console.log ("has layer 1");
                    this.mymap.removeLayer(releves);
                }
            }
        }
    }

图层1在 map 上显示得很好，这里没有问题(参见releves.addTo(this.mymap)).但我有两个问题无法解决:

1. 当我取消选中"Layer 1"(表示else condition part中的event.target.name不是true)时，该层不会被删除，而我使用的是removeLayer方法.
2. hasLayer法似乎不起作用.事实上，在显示了第1层之后，当我取消选中并测试该层是否存在时，我应该得到控制台.删除前记录消息"has layer 1".但什么都没有...

May you know how to debug that ?
Any help would be very appreciated, thanks