> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/llms.txt)
# Animate a line
This example animates a line by updating a GeoJSON source on each frame.
It uses [`addSource`](https://docs.mapbox.com/mapbox-gl-js/api/map/#map#addsource) to add a `GeoJSON` source and uses [`addLayer`](https://docs.mapbox.com/mapbox-gl-js/api/map/#map#addlayer) to add a [`line` layer](https://docs.mapbox.com/style-spec/reference/layers/#line) to the map.
When the animation begins, the data in the GeoJSON object changes, and the line appears animated on the map.
The example [Update a feature in realtime](https://docs.mapbox.com/mapbox-gl-js/example/live-update-feature/) uses a similar approach to create an animation.
> Example code:
**JavaScript**
```html
Animate a line
```
**React**
```jsx
import React, { useEffect, useState, useRef } from 'react';
import * as mapboxgl from 'mapbox-gl/esm';
import 'mapbox-gl/dist/mapbox-gl.css';
const MapboxExample = () => {
const [playback, setPlayback] = useState('Pause');
const mapContainerRef = useRef();
const mapRef = useRef(null);
const animationRef = useRef(null);
const resetTimeRef = useRef(false);
const startTimeRef = useRef(0);
const progressRef = useRef(0);
const geojsonRef = useRef({
type: 'FeatureCollection',
features: [
{
type: 'Feature',
geometry: {
type: 'LineString',
coordinates: [[0, 0]]
}
}
]
});
const speedFactor = 30;
const animateLine = (timestamp) => {
if (resetTimeRef.current) {
startTimeRef.current = performance.now() - progressRef.current;
resetTimeRef.current = false;
} else {
progressRef.current = timestamp - startTimeRef.current;
}
if (progressRef.current > speedFactor * 360) {
startTimeRef.current = timestamp;
geojsonRef.current.features[0].geometry.coordinates = [];
} else {
const x = progressRef.current / speedFactor;
const y = Math.sin((x * Math.PI) / 90) * 40;
geojsonRef.current.features[0].geometry.coordinates.push([x, y]);
mapRef.current.getSource('line').setData(geojsonRef.current);
}
animationRef.current = requestAnimationFrame(animateLine);
};
const handleClick = () => {
if (playback === 'Pause') {
cancelAnimationFrame(animationRef.current);
setPlayback('Play');
} else {
resetTimeRef.current = true;
animateLine();
setPlayback('Pause');
}
};
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',
style: 'mapbox://styles/mapbox/standard',
center: [0, 0],
zoom: 0.5,
projection: 'equalEarth'
});
mapRef.current.on('load', () => {
mapRef.current.addSource('line', {
type: 'geojson',
data: {
type: 'FeatureCollection',
features: [
{
type: 'Feature',
geometry: {
type: 'LineString',
coordinates: [[0, 0]]
}
}
]
}
});
mapRef.current.addLayer({
id: 'line-animation',
type: 'line',
source: 'line',
layout: {
'line-cap': 'round',
'line-join': 'round'
},
paint: {
'line-color': '#ed6498',
'line-width': 5,
'line-opacity': 0.8
}
});
startTimeRef.current = performance.now();
animateLine();
document.addEventListener('visibilitychange', () => {
resetTimeRef.current = true;
});
});
return () => {
if (animationRef.current) {
cancelAnimationFrame(animationRef.current);
}
};
}, []);
return (
);
};
export default MapboxExample;
```