map-script.js

// Once the map loads we push the geoJson over the top.
map.on('load', function() {
    // Power Lines
    var url = 'geojson/power_lines.geojson';
    map.addLayer({
        'id': 'power_lines',
        'type': 'line',
        'source': {                
            'type': 'geojson',
            'data': url
        },
        'paint': {
            'line-color': '#FF5023',
            'line-width': 2,
            'line-dasharray': [1, 1],
        }
    });

});