vue-baidu-map实现区域圈线和路径的渐变色

<bm-polyline
        :path="polylinePath"
        stroke-color="#00ccff"
        :stroke-opacity="1"
        :stroke-weight="2"
        :editing="false"
      ></bm-polyline>
 // 渐变色是在app.vue里面写的
 svg path{
    filter: drop-shadow(2px 4px 6px #00ccff);
}

// 我是把这个方法单独拿出来了，使用的时候引用就好
    getArea(){
      var polyliness = []
      this.polylinePath.forEach((i) => {
        polyliness.push(new this.BMap.Point(i.lng, i.lat));
      });
      var polylinea = new this.BMap.Polyline(polyliness, {strokeColor: "#00ccff", strokeWeight: 1, strokeOpacity: 3});   //创建折线
        //参数：颜色，线的宽度，线的透明度
        this.map.addOverlay(polylinea);
        polylinea.disableMassClear();//这个是防止下面我删除线的时候它不删除
    },

    //添加路线箭头
    getPoly(){
       //创建路线
       var sy = new this.BMap.Symbol(BMap_Symbol_SHAPE_BACKWARD_OPEN_ARROW, {
        scale: 0.6, //图标缩放大小
        strokeColor: "#24a9fa", //设置矢量图标的线填充颜色
        strokeWeight: "2", //设置线宽
      });
      var icons = new this.BMap.IconSequence(sy, "10", "30");
      this.pointList = JSON.parse(JSON.stringify(this.pointList))
     // 创建polyline对象
     var pois = [];
      this.pointList.forEach((i) => {
        pois.push(new this.BMap.Point(i.lng, i.lat));
      });
      // 插入渐变
      // let mapE = document.getElementsByClassName("bm-view")[1];
      setTimeout(()=>{
        let svgE = document.getElementsByTagName("svg")[0];
        console.log("svg",svgE)
        let def = `<defs>
        <linearGradient id="MyGradient">
          <stop offset="0%" stop-color="#2c468b" />
          <stop offset="50%" stop-color="#2f5d95" />
          <stop offset="100%" stop-color="#24a9fa" />
        </linearGradient>
      </defs>`;
      // if (svgE.length==0) {
      //     for(let i in svgE) {
      //       console.log("i",i)
            svgE.insertAdjacentHTML("afterBegin",def);
          // }
        // }
      },1000)
        
      var sj = new this.BMap.Polyline(pois, {
        enableEditing: false, //是否启用线编辑，默认为false
        enableClicking: true, //是否响应点击事件，默认为true
        icons: [icons],
        strokeWeight: "3", //折线的宽度，以像素为单位
        strokeOpacity: 0.8, //折线的透明度，取值范围0 - 1
        strokeColor: "url(#MyGradient)", //折线颜色
        // strokeColor: "red", //折线颜色
      });
      this.map.addOverlay(sj); //增加折线
    },

//调用，在需要调用的地方加上它
setTimeout(()=>{
      this.getPoly()
    },300)