winding problem

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    
    
var width = 1000,
  height = 700;

var svg = d3.select('body')
  .append('svg')
  .attr('width', width)
  .attr('height', height);
    
d3.json('istanbul.geojson', function(error,json) {

console.log(json);

var projection = d3.geoMercator();

var path = d3.geoPath().projection(projection)

projection.fitExtent([[0,0],[width,height]], json);

var areas = json.features.map(function(item){
     							 return d3.geoArea(item)
   								 })

console.log(areas);
  
  svg.selectAll("path").data(json.features)
                        .enter()
                        .append("path")
                        .style("fill","#ccc")
                        .style("stroke","black")
                        .style('opacity', '0.1')
                        .style("stroke-width","2")
                        .attr("d", path)

})

</script>
</body>

https://d3js.org/d3.v4.min.js