> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/ja/llms.txt)
# Add a new layer below labels
This example uses the second argument of [`addLayer`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addlayer) to add a new layer in a precise place in the stack, below the [`symbol` layer](https://docs.mapbox.com/style-spec/reference/layers/#symbol) that contains labels.
The new [`fill` layer](https://docs.mapbox.com/style-spec/reference/layers/#fill) uses an external [`geojson` source](https://docs.mapbox.com/style-spec/reference/sources/#geojson) to add polygon features that are styled with a pink (`#f08`) [`fill-color`](https://docs.mapbox.com/style-spec/reference/layers/#paint-fill-fill-color).
> Example code:
**JavaScript**
```html
Add a new layer below labels
```
**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/streets-v12',
center: [-88.137343, 35.137451],
zoom: 3,
maxZoom: 6
});
mapRef.current.on('load', () => {
const layers = mapRef.current.getStyle().layers;
let firstSymbolId;
for (const layer of layers) {
if (layer.type === 'symbol') {
firstSymbolId = layer.id;
break;
}
}
mapRef.current.addSource('urban-areas', {
type: 'geojson',
data: 'https://docs.mapbox.com/mapbox-gl-js/assets/ne_50m_urban_areas.geojson'
});
mapRef.current.addLayer(
{
id: 'urban-areas-fill',
type: 'fill',
source: 'urban-areas',
layout: {},
paint: {
'fill-color': '#f08',
'fill-opacity': 0.4
}
},
firstSymbolId
);
});
}, []);
return ;
};
export default MapboxExample;
```