Style GeoJSON in react leaflet map library

Question

I have implemented the leaflet map library in my react project https://react-leaflet.js.org/en/ and implemented a geojson map component like below

class MapContainer extends React.Component {
  state = {
    greenIcon: {
      lat: 8.3114,
      lng: 80.4037
    },
    zoom: 8
  };

  grenIcon = L.icon({
    iconUrl: leafGreen,
    iconSize: [24, 24], // size of the icon
    //iconAnchor: [22, 94], // point of the icon which will correspond to marker's location
    popupAnchor: [-3, -16]
  });

  render() {

    const positionGreenIcon = [
      this.state.greenIcon.lat,
      this.state.greenIcon.lng
    ];

    return (
      <div className="mapdata-container">
        <Map className="map" style={{height:'100%',width:'100%'}} center={positionGreenIcon} zoom={this.state.zoom}>
          <GeoJSON data={geo}/>
          <Marker position={positionGreenIcon} icon={this.grenIcon}>
            <Popup>I am a green leaf</Popup>
          </Marker>
        </Map>
      </div>
    );
  }
}

export default MapContainer;

It looks like this

i want to color each province with different colors and there's not alot in the documentation of how to do this.

This is the geojson file i've used. https://raw.githubusercontent.com/thejeshgn/srilanka/master/electoral_districts_map/LKA_electrol_districts.geojson

How do i fill each province with different colors.

Answer 1

You can easily achieve that using style prop on your GeoJSON wrapper. Create a style method which accepts the feature as argument. Then in the fillColor property use the properties: { electoralDistrict } to identify the district and return the desired color: Here is an example of how it could be:

class MapContainer extends React.Component {
  state = {
    greenIcon: {
      lat: 8.3114,
      lng: 80.4037
    },
    zoom: 8
  };

  grenIcon = L.icon({
    iconSize: [24, 24], // size of the icon
    //iconAnchor: [22, 94], // point of the icon which will correspond to marker's location
    popupAnchor: [-3, -16],
    iconUrl: leafGreen
  });

  giveColor = district => {
    switch (district) {
      case "Matara":
        return "red";
      case "Polonnaruwa":
        return "brown";
      case "Ampara":
        return "purple";
      default:
        return "white";
    }
  };

  style = feature => {
    const {
      properties: { electoralDistrict }
    } = feature;
    return {
      fillColor: this.giveColor(electoralDistrict),
      weight: 0.3,
      opacity: 1,
      color: "purple",
      dashArray: "3",
      fillOpacity: 0.5
    };
  };

  render() {
    const positionGreenIcon = [
      this.state.greenIcon.lat,
      this.state.greenIcon.lng
    ];

    return (
      <div className='mapdata-container'>
        <Map
          className='map'
          style={{ height: "100vh", width: "100%" }}
          center={positionGreenIcon}
          zoom={this.state.zoom}
        >
          <GeoJSON data={geo} style={this.style} />
          <Marker position={positionGreenIcon} icon={this.grenIcon}>
            <Popup>I am a green leaf</Popup>
          </Marker>
        </Map>
      </div>
    );
  }
}