<div id ='chart'>
<h3><code>links().linksDisplay();<code></h3>
  <p>Add links from points to points using <code>links()</code> .<code>linksDisplay()</code> customise the appearance of the links.</p>  
</div>  
<div id="elm"></div>

#chart{
  margin: 1em;
}

//RedSift
//projection
//Change projection on viewing the world map.
function whiteLine(selection) {  
    selection.attr('stroke', 'white') //set colour 
             .attr('stroke-width', '2px') //set width
             .attr('stroke-dasharray', '5,3'); //set dash line
}

let geo = d3_rs_geo.html()
                   .links([ [ -76.852587, 38.991621, -0.076132, 51.5074] ,[-0.076132, 51.5074,87.3484, 57.5522] ]) //[longitude,latitude points] forming links
                   .linksDisplay(whiteLine); //customise the links

    d3.select('#elm')
      .datum({ url: 'https://static.redsift.io/thirdparty/topojson/examples/world-50m.json' }) //world topoJSON
      .call(geo);