title: LeafletJS multi-polyline in Typescript
body: <p>I'm trying to use the demo from <a href="http://leafletjs.com/reference-1.2.0.html#polyline" rel="nofollow noreferrer">http://leafletjs.com/reference-1.2.0.html#polyline</a></p>
  
  <pre><code>// create a red polyline from an array of LatLng points
  var latlngs = [
      [45.51, -122.68],
      [37.77, -122.43],
      [34.04, -118.2]
  ];
  var polyline = L.polyline(latlngs, {color: 'red'}).addTo(map);
  // zoom the map to the polyline
  map.fitBounds(polyline.getBounds());
  </code></pre>
  
  <p>However, it's throwing me an error:</p>
  
  <pre><code>[ts]
  Argument of type 'number[][]' is not assignable to parameter of type 'LatLngExpression[]'.
    Type 'number[]' is not assignable to type 'LatLngExpression'.
      Type 'number[]' is not assignable to type '[number, number]'.
        Property '0' is missing in type 'number[]'.
  </code></pre>
  
  <p>is something else needed when using leaflet with Angular/TypeScript?</p>