> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/ja/llms.txt)
# Add a polygon to a map using a GeoJSON source
This example adds a polygon to a map, then colors it blue and makes it slightly transparent.
Upon loading, the map uses [`addSource`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addsource) to add GeoJSON data containing one polygon that outlines the state of Maine. Then it uses [`addLayer`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addlayer) to create a new [fill layer](https://docs.mapbox.com/style-spec/reference/layers/#fill) and applies `paint` properties to style the polygon's appearance. To add an outline around the polygon, it uses `addLayer` again to create a new [line layer](https://docs.mapbox.com/style-spec/reference/layers/#line) referencing the same GeoJSON source.
> Example code:
**JavaScript**
```html
Add a polygon to a map using a GeoJSON source
```
**React**
```jsx
import React, { useEffect, useRef } from 'react';
import * as mapboxgl from 'mapbox-gl/esm';
import 'mapbox-gl/dist/mapbox-gl.css';
const MapboxExample = () => {
const mapContainerRef = useRef();
const mapRef = useRef();
useEffect(() => {
mapRef.current = new mapboxgl.Map({
// TO MAKE THE MAP APPEAR YOU MUST
// ADD YOUR ACCESS TOKEN FROM
// https://account.mapbox.com
accessToken: 'YOUR_MAPBOX_ACCESS_TOKEN',
container: mapContainerRef.current,
style: 'mapbox://styles/mapbox/standard',
config: {
basemap: {
theme: 'monochrome'
}
},
center: [-68.137343, 45.137451],
zoom: 5
});
mapRef.current.on('load', () => {
mapRef.current.addSource('maine', {
type: 'geojson',
data: {
type: 'Feature',
geometry: {
type: 'Polygon',
// These coordinates outline Maine.
coordinates: [
[
[-67.13734, 45.13745],
[-66.96466, 44.8097],
[-68.03252, 44.3252],
[-69.06, 43.98],
[-70.11617, 43.68405],
[-70.64573, 43.09008],
[-70.75102, 43.08003],
[-70.79761, 43.21973],
[-70.98176, 43.36789],
[-70.94416, 43.46633],
[-71.08482, 45.30524],
[-70.66002, 45.46022],
[-70.30495, 45.91479],
[-70.00014, 46.69317],
[-69.23708, 47.44777],
[-68.90478, 47.18479],
[-68.2343, 47.35462],
[-67.79035, 47.06624],
[-67.79141, 45.70258],
[-67.13734, 45.13745]
]
]
}
}
});
mapRef.current.addLayer({
id: 'maine',
type: 'fill',
source: 'maine',
layout: {},
paint: {
'fill-color': '#0080ff',
'fill-opacity': 0.5
}
});
mapRef.current.addLayer({
id: 'outline',
type: 'line',
source: 'maine',
layout: {},
paint: {
'line-color': '#000',
'line-width': 3
}
});
});
}, []);
return ;
};
export default MapboxExample;
```