mapbox layer toggle

<!DOCTYPE html>
<html>
<head>
    <meta charset='utf-8' />
    <title>Show and hide layers</title>
    <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
    <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.48.0/mapbox-gl.js'></script>
    <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.48.0/mapbox-gl.css' rel='stylesheet' />
    <style>
        body { margin:0; padding:0; }
        #map { position:absolute; top:0; bottom:0; width:100%; }
    </style>
</head>
<body>

#menu a {
        font-size: 13px;
        color: #404040;
        display: block;
        margin: 0;
        padding: 0;
        padding: 10px;
        text-decoration: none;
        border-bottom: 1px solid rgba(0,0,0,0.25);
        text-align: center;
    }

#menu a:last-child {
        border: none;
    }

#menu a:hover {
        background-color: #f8f8f8;
        color: #404040;
    }

#menu a.active {
        background-color: #3887be;
        color: #ffffff;
    }

#menu a.active:hover {
        background: #3074a4;
    }
</style>

map.on('load', function () {
    
  map.addSource('watts-curfew-map-dupwjz', {
        type: 'raster',
        url: 'mapbox://andy-rutkowski.0tqu2dvy'
    });
    map.addLayer({
        'id': 'Watts',
        'type': 'raster',
        'source': 'watts-curfew-map-dupwjz',
        'layout': {
            'visibility': 'visible'
        },
        'source-layer': 'watts-curfew-map-dupwjz'
    });

map.addSource('CA_LosAngeles1_193911-3w46o8', {
        type: 'raster',
        url: 'mapbox://andy-rutkowski.cbzfjftf'
    });
    map.addLayer({
        'id': 'HOLC',
        'type': 'raster',
        'source': 'CA_LosAngeles1_193911-3w46o8',
        'source-layer': 'CA_LosAngeles1_193911-3w46o8',
        'layout': {
            'visibility': 'visible',
        },
    });
});

var toggleableLayerIds = [ 'Watts', 'HOLC' ];

for (var i = 0; i < toggleableLayerIds.length; i++) {
    var id = toggleableLayerIds[i];

var link = document.createElement('a');
    link.href = '#';
    link.className = 'active';
    link.textContent = id;

link.onclick = function (e) {
        var clickedLayer = this.textContent;
        e.preventDefault();
        e.stopPropagation();

var visibility = map.getLayoutProperty(clickedLayer, 'visibility');

if (visibility === 'visible') {
            map.setLayoutProperty(clickedLayer, 'visibility', 'none');
            this.className = '';
        } else {
            this.className = 'active';
            map.setLayoutProperty(clickedLayer, 'visibility', 'visible');
        }
    };

var layers = document.getElementById('menu');
    layers.appendChild(link);
}

</script>

</body>
</html>

https://api.tiles.mapbox.com/mapbox-gl-js/v0.48.0/mapbox-gl.js