> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/ja/llms.txt)
# Create a gradient line using an expression
Use the [`line-gradient`](https://docs.mapbox.com/style-spec/reference/layers/#paint-line-line-gradient) paint property and an expression to visualize distance from the starting point of a line.
> Example code:
**JavaScript**
```html
Create a gradient line using an expression
```
**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: [-77.035, 38.875],
zoom: 12
});
const geojson = {
type: 'FeatureCollection',
features: [
{
type: 'Feature',
properties: {},
geometry: {
coordinates: [
[-77.044211, 38.852924],
[-77.045659, 38.860158],
[-77.044232, 38.862326],
[-77.040879, 38.865454],
[-77.039936, 38.867698],
[-77.040338, 38.86943],
[-77.04264, 38.872528],
[-77.03696, 38.878424],
[-77.032309, 38.87937],
[-77.030056, 38.880945],
[-77.027645, 38.881779],
[-77.026946, 38.882645],
[-77.026942, 38.885502],
[-77.028054, 38.887449],
[-77.02806, 38.892088],
[-77.03364, 38.892108],
[-77.033643, 38.899926]
],
type: 'LineString'
}
}
]
};
mapRef.current.on('load', () => {
mapRef.current.addSource('line', {
type: 'geojson',
lineMetrics: true,
data: geojson
});
mapRef.current.addLayer({
type: 'line',
source: 'line',
id: 'line',
paint: {
'line-color': 'red',
'line-width': 14,
'line-gradient': [
'interpolate',
['linear'],
['line-progress'],
0,
'blue',
0.1,
'royalblue',
0.3,
'cyan',
0.5,
'lime',
0.7,
'yellow',
1,
'red'
]
},
layout: {
'line-cap': 'round',
'line-join': 'round'
}
});
});
return () => {
mapRef.current.remove();
};
}, []);
return ;
};
export default MapboxExample;
```