Set max and min zoom for a CartoDB visualization

<!DOCTYPE html>
<html>
  <head>
    <title>Easy example | CartoDB.js</title>
    <meta name="viewport" content="initial-scale=1.0, user-scalable=no" />
    <meta http-equiv="content-type" content="text/html; charset=UTF-8"/>
    <link rel="shortcut icon" href="https://cartodb.com/assets/favicon.ico" />
    <style> html, body, #map { height:100%; padding:0; margin:0 } </style>
    <link rel="stylesheet" href="https://libs.cartocdn.com/cartodb.js/v3/themes/css/cartodb.css" />
  </head>
  <body>
    <div id="map"></div>
    
    
    <script src="https://libs.cartocdn.com/cartodb.js/v3/cartodb.js"></script>

cartodb.createVis('map', url, {
          search: true,
          tiles_loader: true,
          layer_selector: true,
          https: true
        })
        .done(function(vis, layers) {

// Set max zoom
          vis.map.set({
            minZoom: 3,
            maxZoom: 6
          });

})
        .error(function(err) {
          console.log(err);
        });
      }
 
      window.onload = main;
    </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