Leaflet layer geojson self cleaning on zoom out

L.GeoJSONAutoClear.js

L.GeoJSONAutoClear = L.GeoJSON.extend({
	options: {
		autoclear: true,
		zoomdiff: 2
	},
	_autoClear: function(e) {
		if(this.getLayers().length) {
			if(e.target.getZoom() < e.target.getBoundsZoom(this.getBounds())-this.options.zoomdiff)
				this.clearLayers();
		}
	},
	onAdd: function(map) {
		
		L.GeoJSON.prototype.onAdd.call(this, map);

		if(this.options.autoclear)
			map.on('zoomend', this._autoClear, this);
	},
	onRemove: function(map) {
		
		L.GeoJSON.prototype.onRemove.call(this, map);

		if(this.options.autoclear)
			map.off('zoomend', this._autoClear, this);
	}
});