Example showing how to load layers in Cartodb and turn them on / off.

<!DOCTYPE html>
    
    
    
     <html class="no-js"> 
    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
        <title>CartoDB.JS Demo</title>
        <meta name="description" content="">
        <meta name="HandheldFriendly" content="True">
        <meta name="MobileOptimized" content="320">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <meta http-equiv="cleartype" content="on">
        <style type="text/css">

html, body, #map {
            height: 100%;
            padding: 0;
            margin: 0;
          }
          
          ul {
            position: absolute;
            top: 5%; right: 5%;
          }

li {
            margin: -1px;
            padding: 10px;
            border: 1px solid #fff;
            background: #000;
            list-style: none;            
            font: bold 16pt helvetica;
            color: #fff;
            text-align: center;
            letter-spacing: 1px;
          }

a {
            text-decoration: none;
            color: #fff;
          }

#bike-routes {
            
          }

#truck-routes {

}

</style>
        <link rel="stylesheet" href="https://libs.cartocdn.com/cartodb.js/v3/themes/css/cartodb.css" />
    </head>
    <body>

<div id="map"></div>
        <div id="layer-control">
          <ul>
            <li id="bike-routes"><a href="#">Bicycle Routes</a></li>
            <li id="truck-routes"><a href="#">Truck Routes</a></li>
          </ul>
        </div>
        
        
        <script src="https://libs.cartocdn.com/cartodb.js/v3/cartodb.js"></script>
        <script type="text/javascript">

// set up the leaflet map object 
          var map = new L.Map('map', {
            center: [40.7127, -74.0059],
            zoom: 12
          });

// variables to store cartodb layers in later
          var bike_routes = null,
                truck_routes = null;

/* add the Stamen Toner basemap layer */
          L.tileLayer('https://tile.stamen.com/toner/{z}/{x}/{y}.png', {
            attribution: 'Stamen'
          }).addTo(map);

// instantiate some cartodb layers
          var cartodbLayers = cartodb.createLayer(map, {
            user_name: 'chenrick',
            type: 'cartodb',
            sublayers: [{
              sql : 'SELECT * FROM nyc_bike_routes_4326',
              cartocss : '#nyc_bike_routes_4326 { line-width: 2; line-color: #00a9ff; }'
            }, {
              sql : 'SELECT * FROM all_truck_routes_nyc_2011_april',
              cartocss : '#all_truck_routes_nyc_2011_april { line-width: 2; line-color: #ff0098; }'
            }]
          })
            .on('done', function(layer){                            
              bike_routes = layer.getSubLayer(0); // assign the bike routes layer
              truck_routes = layer.getSubLayer(1); // assign the truck routes layer             
            })
           .addTo(map); // add them to the map

/* UI interaction*/
          // state variable for layer visibility
          var visible = {
            bikes : true,
            trucks : true
          };

// bike button toggle
          $('#bike-routes').on('click', function(e) {              
            if (visible.bikes){
              bike_routes.hide();
              visible.bikes = false;
            } else if (!visible.bikes){ 
              bike_routes.show();
              visible.bikes = true;              
            }
            return false;       
          });

// truck button toggle
          $('#truck-routes').on('click', function(e) {
            if (visible.trucks) {
              truck_routes.hide();
              visible.trucks = false;
            } else if (!visible.trucks) {
              truck_routes.show();
              visible.trucks = true;              
            }
            return false;
          });

</script>

</body>
</html>

Modified http://libs.cartocdn.com/cartodb.js/v3/cartodb.js to a secure url

https://libs.cartocdn.com/cartodb.js/v3/cartodb.js