Add a vector tile source | Mapbox GL JS

Add a vector source to a map.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Add a vector tile source</title>
<meta name="viewport" content="initial-scale=1,maximum-scale=1,user-scalable=no">
<link href="https://api.mapbox.com/mapbox-gl-js/v2.1.1/mapbox-gl.css" rel="stylesheet">
<script src="https://api.mapbox.com/mapbox-gl-js/v2.1.1/mapbox-gl.js"></script>
<style>
body { margin: 0; padding: 0; }
#map { position: absolute; top: 0; bottom: 0; width: 100%; }
</style>
</head>
<body>
<div id="map"></div>
<script>
	// TO MAKE THE MAP APPEAR YOU MUST
	// ADD YOUR ACCESS TOKEN FROM
	// https://account.mapbox.com
	mapboxgl.accessToken = '<your access token here>';
var map = new mapboxgl.Map({
container: 'map',
style: 'mapbox://styles/mapbox/light-v10',
zoom: 13,
center: [-122.447303, 37.753574]
});
 
map.on('load', function () {
map.addSource('mapbox-terrain', {
type: 'vector',
url: 'mapbox://mapbox.mapbox-terrain-v2'
});
map.addLayer({
'id': 'terrain-data',
'type': 'line',
'source': 'mapbox-terrain',
'source-layer': 'contour',
'layout': {
'line-join': 'round',
'line-cap': 'round'
},
'paint': {
'line-color': '#ff69b4',
'line-width': 1
}
});
});
</script>
 
</body>
</html>