Getting the bounds of loaded tile of leaflet - leaflet

Question

Using leaflet is there any way I can get the bounds (NorthEast, SouthWest) of a loaded tile? I want to request the server to load the markers only for a particular tile which is loaded, so that when user is panning/dragging the map he can easily see the new markers on new area.

Answer 1

What you really want to do is a subclass of L.GridLayer. This will allow fine control over loaded/unloaded tiles, and is the best way to use the private L.GridLayer._tileCoordsToBounds() method.
With some basic handling of loaded markers, it should look like:
L.GridLayer.MarkerLoader = L.GridLayer.extend({
onAdd: function(map){
// Add a LayerGroup to the map, to hold the markers
this._markerGroup = L.layerGroup().addTo(map);
L.GridLayer.prototype.onAdd.call(this, map);
// Create a tilekey index of markers
this._markerIndex = {};
},
onRemove: function(map){
this._markergroup.removeFrom(map);
L.GridLayer.prototype.onRemove.call(this, map);
};
createTile: function(coords, done) {
var tileBounds = this._tileCoordsToBounds(coords);
var tileKey = this._tileCoordsToKey(coords);
var url = ...; // Compute right url using tileBounds & coords.z
fetch(url).then(function(res){
if (!key in this._markerIndex) { this._markerIndex[key] = []; }
// unpack marker data from result, instantiate markers
// Loop as appropiate
this._markerGroup.addLayer(marker);
this._markerIndex[key] = marker;
done(); // Signal that the tile has been loaded successfully
});
},
_removeTile: function (key) {
for (var i in this._markerIndex[key]) {
this._markerGroup.remove(this._markerIndex[key][i]);
}
L.GridLayer.prototype._removeTile.call(this, key);
}
});
Please note that zooming might be a source of bugs and graphical glitches (markers being removed because a tile unloads, before the markers at the new zoom level are loaded). Beware of that.