topojson on a map: buffers by almccon

index.html

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <meta name='viewport' content='initial-scale=1,maximum-scale=1,user-scalable=no' />
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <script src="//d3js.org/topojson.v1.min.js"></script>
  
  <script src='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.js'></script>
  <link href='https://api.tiles.mapbox.com/mapbox-gl-js/v0.12.0/mapbox-gl.css' rel='stylesheet' />
  
  <script src="https://cdnjs.cloudflare.com/ajax/libs/Turf.js/2.0.2/turf.min.js"></script>

  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    #map { 
      position:absolute; 
      width: 100%;
      height: 100%;
    }
    svg {
      position: absolute;
      width: 100%;
      height: 100%;
    }
    .land {
      stroke: #111;
      stroke-opacity: 1;
      fill: #efe93d;
      fill-opacity: 0.1;
    }
    .river {
      stroke: #111;
      fill: none;
      stroke-width: 1px;
    }
    .caption {
      background-color: rgba(100, 200, 200, 0.8);
      border: 1px solid #444;
      position: fixed;
      top: 20px;
      left: 20px;
      padding: 8px;
    }
  </style>
</head>

<body>
  <div id="map"></div>
  <div class="caption"></div>
  <script>
  
    mapboxgl.accessToken = 'pk.eyJ1IjoiZW5qYWxvdCIsImEiOiJjaWhtdmxhNTIwb25zdHBsejk0NGdhODJhIn0.2-F2hS_oTZenAWc0BMf_uw'
    
    //Setup mapbox-gl map
    var map = new mapboxgl.Map({
      container: 'map', // container id
      style: 'mapbox://styles/enjalot/cihmvv7kg004v91kn22zjptsc',
      center: [-0.1,51.5119112],
      zoom: 11.5,
      
    })
    map.scrollZoom.disable()
    map.addControl(new mapboxgl.Navigation());

    // Setup our svg layer that we can manipulate with d3
    var container = map.getCanvasContainer()
    var svg = d3.select(container).append("svg")
    
    var path = d3.geo.path()
    .projection(function(lonlat, i) {
      var p = map.project(new mapboxgl.LngLat(lonlat[0], lonlat[1]))
      return [p.x, p.y];

    })
  
    d3.json("london-neighborhoods.topojson", function(err, london) {
    d3.json("london-rivers.topojson", function(err, rivers) {
      //console.log(london.objects['london-neighborhoods-slim'])
      var neighborhoods = topojson.feature(london, london.objects['london-neighborhoods-slim']);
      var buffered = buffer(neighborhoods, -0.0005, 'degrees')
      
      var riverFeatures = topojson.feature(rivers, rivers.objects['london-rivers']);
      var thames = getThames(riverFeatures, 80, 'meters')
      //var buffered = buffer(features, -0.0005, 'degrees')
      
      //var sliced = difference(neighborhoods, thames)
      //console.log("sliced", sliced)
      //console.log("original", features)
      //console.log("buffered", buffered)
      
      var land = svg.append("path")
        .datum(buffered)
        .attr("class", "land")
        .attr("d", path);
      
      /*
      var riversvg = svg.append("path")
        .datum(thames)
        .attr("class", "river")
        .attr("d", path);
      */
      function render() {
       
        land.attr("d", path)
        //riversvg.attr("d", path)
      }

      // re-render our visualization whenever the view changes
      map.on("viewreset", function() {
        render()
      })
      map.on("move", function() {
        render()
      })

      // render our initial visualization
      render();
      
      map.on("click", function(e) {
        console.log("click", e);
        var p = {
          'type': 'Feature',
          'geometry': {
            'type': 'Point',
            'coordinates': [e.lngLat.lng, e.lngLat.lat]
          }
        };
        features.features.forEach(function(feature) {
        //buffered.features.forEach(function(feature) {
           var isInside = turf.inside(p, feature);  
          if(isInside) { 
            console.log(feature);
            d3.select(".caption").text(feature.properties.name)
          }
        })
        
      })
    }) })
    
    // from //blockbuilder.org/armollica/c6c97710ac404e67b6bf
    function buffer(featureCollection, distance, unit) {
      var features = featureCollection.features
        .map(function(feature) {
          var buffered = null;
          try { 
            buffered = turf.buffer(feature, distance, unit).features[0];
            buffered.properties = feature.properties;
          } catch(e) {  console.error(e);  }
          return buffered;
        })
        .filter(function(feature) { return feature !== null; });

      return {
        type: "FeatureCollection",
        features: features,
        properties: null
      };
    }
    
    function getThames(featureCollection, distance, unit) {
      var thames = featureCollection.features.filter(function(feature) {
        if(feature.properties.name === "River Thames")
          return true;
        return false;
      })
      console.log("thames", thames);
      var fc = {
        type: "FeatureCollection",
        features: thames,
        properties: null
      };
      return buffer(fc, distance, unit)
    }
    
    function difference(fcA, fcB) {
      var features = [];
      fcA.features.forEach(function(a) {
        fcB.features.forEach(function(b) {
          try {
            var diff = turf.erase(a,b);
            features.push(diff);
          } catch(e) {
          }
        })
      })
      return {
        type: "FeatureCollection",
        features: features,
        properties: null
      }
    }

    
  </script>
</body>