> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/llms.txt)
# Visualize population density
Use a [variable binding expression](https://docs.mapbox.com/style-spec/reference/expressions/#variable-binding) to calculate and display population density.
> Example code:
**JavaScript**
```html
Visualize population density
```
**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',
center: [30.0222, -1.9596],
zoom: 7
});
mapRef.current.on('load', () => {
mapRef.current.addSource('rwanda-provinces', {
type: 'geojson',
data: 'https://docs.mapbox.com/mapbox-gl-js/assets/rwanda-provinces.geojson'
});
mapRef.current.addLayer({
id: 'rwanda-provinces',
type: 'fill',
source: 'rwanda-provinces',
layout: {},
paint: {
'fill-color': [
'let',
'density',
['/', ['get', 'population'], ['get', 'sq-km']],
[
'interpolate',
['linear'],
['zoom'],
8,
[
'interpolate',
['linear'],
['var', 'density'],
274,
['to-color', '#f5e5f3'],
1551,
['to-color', '#8d00ac']
],
10,
[
'interpolate',
['linear'],
['var', 'density'],
274,
['to-color', '#eff3ff'],
1551,
['to-color', '#08519c']
]
]
],
'fill-opacity': 0.7
},
slot: 'middle'
});
});
return () => {
mapRef.current.remove();
};
}, []);
return ;
};
export default MapboxExample;
```