leaflet@1.5.1 & d3@5.0.0 - ポリゴン表示表示

leaflet@1.5.1 と d3@5.0.0 を使って地図上にポリゴンを表示するサンプル

<!DOCTYPE html>
<html>

<head>
<title>Leafletv1.5.1 + D3v5 point</title>
<meta charset="utf-8" />

<link rel="stylesheet" href="https://unpkg.com/leaflet@1.5.1/dist/leaflet.css"
    integrity="sha512-xwE/Az9zrjBIphAcBb3F6JVqxf46+CDLwfLMHloNu6KEQCAWi6HcDUbeOfBIptF7tcCzusKFjFw2yuvEpDL9wQ=="
    crossorigin="" />

<script src="https://unpkg.com/leaflet@1.5.1/dist/leaflet.js"
    integrity="sha512-GffPMF3RvMeYyc1LWMHtK8EbPv0iNZ8/oTtHPx9/cc2ILxQ+u905qIwdpULaqDkyBKgOaB57QTMg7ztg8Jm2Og=="
    crossorigin=""></script>

<script src='//unpkg.com/d3@5.0.0/dist/d3.min.js'></script>
    <script>
    //Leaflet初期設定
    var map = L.map('map').setView([39.702053, 141.15448379999998], 5);
    var mapLink = '<a target="_blank" href="https://portal.cyberjapan.jp/help/termsofuse.html">国土地理院 地理院地図 標準地図</a>';

//Leafletにsvgレイヤーを追加
    L.svg().addTo(map);

//Tile Map Serviceの指定
    L.tileLayer('https://cyberjapandata.gsi.go.jp/xyz/std/{z}/{x}/{y}.png', {
        attribution: '&copy; ' + mapLink + ' Contributors',
        maxZoom: 18
    }).addTo(map);

d3.json('pref.geojson').then(drawMap);

function drawMap(geojson) {
        // svg要素を選択
        var svg = d3.select('#map').select('svg');
        var g = svg.append('g');

//緯度経度->パスジェネレーター関数作成
        //位置→座標変換
        var projectPoint = function (x, y) {
            var point = map.latLngToLayerPoint(new L.LatLng(y, x));
            this.stream.point(point.x, point.y);
        };
        var transform = d3.geoTransform({ point: projectPoint });
        var path = d3.geoPath().projection(transform);

featureElement = g
            .selectAll('path')
            .data(geojson.features)
            .enter()
            .append('path')
            .attr('stroke', 'red')
            .attr('fill', 'green')
            .attr('fill-opacity', 0.4);

//pathのd属性を更新
        var update = function () {
            featureElement.attr('d', path);
        };

map.on('moveend', update);
        update();
    }
    
    </script>
</body>

</html>

https://unpkg.com/d3@5.0.0/dist/d3.min.js