Leaflet: First Map

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    <link rel='stylesheet' href='https://leafletjs.com/dist/leaflet.css'>
    
    <script src='https://leafletjs.com/dist/leaflet.js' type='text/javascript'></script>
    
    <style>
    .rChart {
      display: block
      margin: auto auto;
      width: 800px;
      height: 400px;
    }
    body {
      margin-top: 60px;
    }
    </style>
    
  </head>
  <body>
    <div class='container'>
      <div class='row'>
        <div class='span9'>
          <div id='chartfa9e689dfefb' class='rChart nvd3Plot leaflet'></div>
          <br/>
<pre><code class='r'>require(rCharts)
map1 = Leaflet$new()
map1$setView(45.5236, -122.675, 4)
map1$tileLayer(&quot;https://a.tiles.mapbox.com/v3/mapbox.control-room/{z}/{x}/{y}.png&quot;, 8)
map1
</code></pre>
        </div>
      </div>
    </div>
      
    <script>
  var spec = {
 "dom": "chartfa9e689dfefb",
"width":    800,
"height":    400,
"center": [
 45.524,
-122.67 
],
"viewOpts": [
      4 
],
"urlTemplate": "https://a.tiles.mapbox.com/v3/mapbox.control-room/{z}/{x}/{y}.png",
"layerOpts": {
 "":      8,
"attribution": "Map data © <a href=\"https://openstreetmap.org\">OpenStreetMap</a>contributors, Imagery © <a href=\"https://mapbox.com\">MapBox</a>" 
},
"id": "chartfa9e689dfefb" 
}
  var map = L.map(spec.dom)
    .setView(spec.center, spec.viewOpts);

L.tileLayer(spec.urlTemplate, spec.layerOpts)
     .addTo(map);

/*
		L.marker([51.5, -0.09]).addTo(map)
			.bindPopup("<b>Hello world!</b><br />I am a popup.").openPopup();
      
    L.marker([51.52, -0.09]).addTo(map)
			.bindPopup("<b>Hello world!</b><br />I am a popup.").openPopup();

L.circle([51.508, -0.11], 500, {
			color: 'red',
			fillColor: '#f03',
			fillOpacity: 0.5
		}).addTo(map).bindPopup("I am a circle.");

L.polygon([
			[51.509, -0.08],
			[51.503, -0.06],
			[51.51, -0.047]
		]).addTo(map).bindPopup("I am a polygon.");

var popup = L.popup();

function onMapClick(e) {
			popup
				.setLatLng(e.latlng)
				.setContent("You clicked the map at " + e.latlng.toString())
				.openOn(map);
		}

map.on('click', onMapClick);
    */

</script>
    
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Modified http://leafletjs.com/dist/leaflet.js to a secure url

Modified http://cdnjs.cloudflare.com/ajax/libs/prettify/188.0.0/prettify.js to a secure url

https://leafletjs.com/dist/leaflet.js

https://cdnjs.cloudflare.com/ajax/libs/prettify/188.0.0/prettify.js