如何获取可视范围的数据呢？首先我们要捕获到地图对角线的经纬度。我们可以用uniapp自带uni.createMapContext(mapId,this)来获取

regionchange() {
    let map = uni.createMapContext('map');
    map.getRegion({
         success: res => {
             let obj = {
                  latitude: JSON.stringify([{
                      min: res.southwest.latitude.toString(),
                      max: res.northeast.latitude.toString()
                  }]),
                  longitude: JSON.stringify([{
                      min: res.southwest.longitude.toString(),
                      max: res.northeast.longitude.toString()
                  }])
             }
             this.getMarks(obj);//捕获到对角线经纬度后，调用方法传参给后端
         },
         fail: (data, code) => {
               console.log('fail' + JSON.stringify(data));
         }
    })
}