--- layout: tutorial title: Using GeoJSON with Leaflet ---

### Using GeoJSON with Leaflet

GeoJSON is becoming a very popular data format among many GIS technologies and services — it's simple, lightweight, straightforward, and Leaflet is quite good at handling it. In this example, you'll learn how to create and interact with map vectors created from GeoJSON objects.

View example on a separate page →

### About GeoJSON

According to http://geojson.org:

> GeoJSON is a format for encoding a variety of geographic data structures. A GeoJSON object may represent a geometry, a feature, or a collection of features. GeoJSON supports the following geometry types: Point, LineString, Polygon, MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection. Features in GeoJSON contain a geometry object and additional properties, and a feature collection represents a list of features.

Leaflet supports all of the GeoJSON types above, but Features and FeatureCollections work best as they allow you to describe features with a set of properties. We can even use these properties to style our Leaflet vectors. Here's an example of a simple GeoJSON feature:

    var geojsonFeature = {
    	"type": "Feature",
    	"properties": {
    		"name": "Coors Field",
    		"amenity": "Baseball Stadium",
    		"popupContent": "This is where the Rockies play!"
    	},
    	"geometry": {
    		"type": "Point",
    		"coordinates": [-104.99404, 39.75621]
    	}
    };

### The GeoJSON layer

GeoJSON objects are added to the map through a GeoJSON layer. To create it and add it to a map, we can use the following code:

    L.geoJson(geojsonFeature).addTo(map);

GeoJSON objects may also be passed as an array of valid GeoJSON objects.

    var myLines = [{
    	"type": "LineString",
    	"coordinates": [[-100, 40], [-105, 45], [-110, 55]]
    }, {
    	"type": "LineString",
    	"coordinates": [[-105, 40], [-110, 45], [-115, 55]]
    }];

Alternatively, we could create an empty GeoJSON layer and assign it to a variable so that we can add more features to it later.

    var myLayer = L.geoJson().addTo(map);
    myLayer.addData(geojsonFeature);

### Options

#### style

The `style` option can be used to style features two different ways. First, we can pass a simple object that styles all paths (polylines and polygons) the same way:

    var myLines = [{
    	"type": "LineString",
    	"coordinates": [[-100, 40], [-105, 45], [-110, 55]]
    }, {
    	"type": "LineString",
    	"coordinates": [[-105, 40], [-110, 45], [-115, 55]]
    }];

    var myStyle = {
    	"color": "#ff7800",
    	"weight": 5,
    	"opacity": 0.65
    };

    L.geoJson(myLines, {
    	style: myStyle
    }).addTo(map);

Alternatively, we can pass a function that styles individual features based on their properties. In the example below we check the "party" property and style our polygons accordingly:

    var states = [{
    	"type": "Feature",
    	"properties": {"party": "Republican"},
    	"geometry": {
    		"type": "Polygon",
    		"coordinates": [[
    			[-104.05, 48.99],
    			[-97.22,  48.98],
    			[-96.58,  45.94],
    			[-104.03, 45.94],
    			[-104.05, 48.99]
    		]]
    	}
    }, {
    	"type": "Feature",
    	"properties": {"party": "Democrat"},
    	"geometry": {
    		"type": "Polygon",
    		"coordinates": [[
    			[-109.05, 41.00],
    			[-102.06, 40.99],
    			[-102.03, 36.99],
    			[-109.04, 36.99],
    			[-109.05, 41.00]
    		]]
    	}
    }];

    L.geoJson(states, {
    	style: function(feature) {
    		switch (feature.properties.party) {
    			case 'Republican': return {color: "#ff0000"};
    			case 'Democrat':   return {color: "#0000ff"};
    		}
    	}
    }).addTo(map);

#### pointToLayer

Points are handled differently than polylines and polygons. By default simple markers are drawn for GeoJSON Points. We can alter this by passing a `pointToLayer` function in a GeoJSON options object when creating the GeoJSON layer. This function is passed a LatLng and should return an instance of ILayer, in this case likely a Marker or CircleMarker.

Here we're using the `pointToLayer` option to create a CircleMarker:

    var geojsonMarkerOptions = {
    	radius: 8,
    	fillColor: "#ff7800",
    	color: "#000",
    	weight: 1,
    	opacity: 1,
    	fillOpacity: 0.8
    };

    L.geoJson(someGeojsonFeature, {
    	pointToLayer: function (feature, latlng) {
    		return L.circleMarker(latlng, geojsonMarkerOptions);
    	}
    }).addTo(map);

We could also set the `style` property in this example — Leaflet is smart enough to apply styles to GeoJSON points if you create a vector layer like circle inside the `pointToLayer` function.

#### onEachFeature

The `onEachFeature` option is a function that gets called on each feature before adding it to a GeoJSON layer. A common reason to use this option is to attach a popup to features when they are clicked.

    function onEachFeature(feature, layer) {
    	// does this feature have a property named popupContent?
    	if (feature.properties && feature.properties.popupContent) {
    		layer.bindPopup(feature.properties.popupContent);
    	}
    }

    var geojsonFeature = {
    	"type": "Feature",
    	"properties": {
    		"name": "Coors Field",
    		"amenity": "Baseball Stadium",
    		"popupContent": "This is where the Rockies play!"
    	},
    	"geometry": {
    		"type": "Point",
    		"coordinates": [-104.99404, 39.75621]
    	}
    };

    L.geoJson(geojsonFeature, {
    	onEachFeature: onEachFeature
    }).addTo(map);

#### filter

The `filter` option can be used to control the visibility of GeoJSON features. To accomplish this we pass a function as the `filter` option. This function gets called for each feature in your GeoJSON layer, and gets passed the `feature` and the `layer`. You can then utilise the values in the feature's properties to control the visibility by returning `true` or `false`.

In the example below "Busch Field" will not be shown on the map.

    var someFeatures = [{
    	"type": "Feature",
    	"properties": {
    		"name": "Coors Field",
    		"show_on_map": true
    	},
    	"geometry": {
    		"type": "Point",
    		"coordinates": [-104.99404, 39.75621]
    	}
    }, {
    	"type": "Feature",
    	"properties": {
    		"name": "Busch Field",
    		"show_on_map": false
    	},
    	"geometry": {
    		"type": "Point",
    		"coordinates": [-104.98404, 39.74621]
    	}
    }];

    L.geoJson(someFeatures, {
    	filter: function(feature, layer) {
    		return feature.properties.show_on_map;
    	}
    }).addTo(map);

View the example page to see in detail what is possible with the GeoJSON layer.