Edit in JSFiddle 
<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
        <title>Basic Maps</title>

        <link href="https://tiles.locationiq.com/v3/libs/leaflet/1.8.0/leaflet.css" rel="stylesheet" type="text/css"/>
        <script type="text/javascript" src="https://tiles.locationiq.com/v3/libs/leaflet/1.8.0/leaflet.js"></script>
        <script type="text/javascript" src="https://tiles.locationiq.com/v3/js/liq-styles-ctrl-leaflet.js?v=0.1.8"></script>
        
        <style type="text/css">
            body {
                margin: 0;
            }
            #map {
                width: 100vw;
                height: 100vh;
            }
        </style>
    </head>

    <body>
        <div id='map'></div>
        <script type="text/javascript">
            // Maps access token goes here
            var key = 'pk.aa7f5d0539c5675b7f3429402939d8fa';

            // Add layers that we need to the map
            var streets = L.tileLayer.Unwired({key: key, scheme: "streets"});

            // Initialize the map
            var map = L.map('map', {
                center: [39.73, -104.99], // Map loads with this location as center
                zoom: 14,
                scrollWheelZoom: false,
                layers: [streets]         // Show 'streets' by default
            });

            // Add the 'scale' control
            L.control.scale().addTo(map);

            // Add the 'layers' control
            L.control.layers({
                "Streets": streets
            }).addTo(map);

        </script>
    </body>
</html>