> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/ja/llms.txt)
# Generate and add a missing icon to the map
This example uses [`addLayer`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addlayer) to add a layer to a [style](https://docs.mapbox.com/help/glossary/style/), but it references an image that does not exist in the style's [sprite](https://docs.mapbox.com/help/glossary/sprite/) or list of available images. Since the image is missing, the property that references the image throws a [`styleimagemissing`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map.event:styleimagemissing) event.
This example uses that `styleimagemissing` event to detect the missing image, then it generates a new image and adds that image to the map style with [`addImage`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addimage) within the event listener callback to make sure that an icon is rendered even if the referenced image is missing.
> Example code:
**JavaScript**
```html
Generate and add a missing icon to the map
```
**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: 'map',
center: [0, 0],
zoom: 2,
style: 'mapbox://styles/mapbox/standard'
});
mapRef.current.on('styleimagemissing', (e) => {
const id = e.id; // id of the missing image
// Check if this missing icon is
// one this function can generate.
const prefix = 'square-rgb-';
if (!id.includes(prefix)) return;
// Get the color from the id.
const rgb = id.replace(prefix, '').split(',').map(Number);
const width = 64; // The image will be 64 pixels square.
const bytesPerPixel = 4; // Each pixel is represented by 4 bytes: red, green, blue, and alpha.
const data = new Uint8Array(width * width * bytesPerPixel);
for (let x = 0; x < width; x++) {
for (let y = 0; y < width; y++) {
const offset = (y * width + x) * bytesPerPixel;
data[offset + 0] = rgb[0]; // red
data[offset + 1] = rgb[1]; // green
data[offset + 2] = rgb[2]; // blue
data[offset + 3] = 255; // alpha
}
}
mapRef.current.addImage(id, { width: width, height: width, data: data });
});
mapRef.current.on('load', () => {
mapRef.current.addSource('points', {
type: 'geojson',
data: {
type: 'FeatureCollection',
features: [
{
type: 'Feature',
geometry: {
type: 'Point',
coordinates: [0, 0]
},
properties: {
color: '255,0,0'
}
},
{
type: 'Feature',
geometry: {
type: 'Point',
coordinates: [50, 0]
},
properties: {
color: '255,209,28'
}
},
{
type: 'Feature',
geometry: {
type: 'Point',
coordinates: [-50, 0]
},
properties: {
color: '242,127,32'
}
}
]
}
});
mapRef.current.addLayer({
id: 'points',
type: 'symbol',
source: 'points',
layout: {
'icon-image': ['concat', 'square-rgb-', ['get', 'color']]
}
});
});
}, []);
return ;
};
export default MapboxExample;
```