// 例: GeoJSONファイルを leaflet-ajax でロードする
var jsonmap = L.map("load-json").setView([38.891, 139.824], 16);
var layer = L.tileLayer(
    'https://cyberjapandata.gsi.go.jp/xyz/std/{z}/{x}/{y}.png',
    {attribution:
     '&copy; <a href="//www.gsi.go.jp/kikakuchousei/kikakuchousei40182.html">国土地理院</a>'
    }).addTo(jsonmap);
var gjl = new L.GeoJSON.AJAX("triangle-load.geojson",{
    onEachFeature: function(j, layer) {
	let p = j.properties;
	if (p) {
	    let name = p.name, desc = p.description;
	    let popup = "<h3>" + name + "</h3>" + "<p>" + desc + "</p>";
	    layer.bindPopup(popup);
	}
    }});
gjl.addTo(jsonmap);
gjl.on('data:loaded', function() {
    jsonmap.fitBounds(gjl.getBounds());
});
L.control.layers(null, {"Triangle": gjl}).addTo(jsonmap);