nrenner/MyHash.js

## index.html
<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>Extending leaflet-fullHash</title>

    <link href="https://unpkg.com/leaflet@1.0.0/dist/leaflet.css" rel="stylesheet" type="text/css" />
    <script src="https://unpkg.com/leaflet@1.0.0/dist/leaflet-src.js"></script>
    <script src="http://kogor.github.io/leaflet-fullHash/leaflet-fullHash.js"></script>
    <script src="MyHash.js"></script>

    <style>
        #map {
            width: 600px;
            height: 400px;
        }
    </style>
</head>

<body>
    <div id='map'></div>

    <script>
        var myCenter = new L.LatLng(50.5, 30.51);
        var map = new L.Map('map', { center: myCenter, zoom: 15 });

        var osmCopy = '&copy; <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors';
        map.attributionControl.addAttribution(osmCopy);
        var osm = L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png');
        var positron = L.tileLayer('https://cartodb-basemaps-{s}.global.ssl.fastly.net/light_all/{z}/{x}/{y}.png', {
            attribution: '&copy; <a href="https://carto.com/attribution">CARTO</a>'
        }).addTo(map);

        var marker = new L.Marker(myCenter);
        map.addLayer(marker);
        marker.bindPopup("<p>Lorem ipsum dolor sit amet</p>");

        L.control.layers({
            'OpenStreetMap Standard': osm,
            'Carto Positron': positron
        }, {
            'Marker': marker
            }
        ).addTo(map);


        var layerHashKeys = {
            'osm': osm,
            'positron': positron,
            'marker': marker
        };
        L.myHash(map, layerHashKeys);

    </script>
</body>

</html>

## MyHash.js
L.MyHash = function(map, options) {
    L.Hash.call(this, map, options);
};

L.MyHash.prototype = L.Util.create(L.Hash.prototype);
L.MyHash.prototype.constructor = L.MyHash;

L.Util.extend(L.MyHash.prototype, {
    parseHash: function(hash) {
        console.log('parseHash: ' + hash);
        var parsed = L.Hash.prototype.parseHash.call(this, hash);
        console.log('parseHash: ' + JSON.stringify(parsed));
        return parsed;
    },

    formatHash: function(map) {
        var formatted = L.Hash.prototype.formatHash.call(this, map);
        console.log('formatHash: ' + formatted);
        return formatted;
    },

    update: function() {
        L.Hash.prototype.update.call(this);
        console.log('update');
    }
});

L.myHash = function(map, options) {
	return new L.MyHash(map, options);
};
	<!DOCTYPE html>
	<html>

	<head>
	<meta charset="utf-8">
	<title>Extending leaflet-fullHash</title>

	<link href="https://unpkg.com/leaflet@1.0.0/dist/leaflet.css" rel="stylesheet" type="text/css" />
	<script src="https://unpkg.com/leaflet@1.0.0/dist/leaflet-src.js"></script>
	<script src="http://kogor.github.io/leaflet-fullHash/leaflet-fullHash.js"></script>
	<script src="MyHash.js"></script>

	<style>
	#map {
	width: 600px;
	height: 400px;
	}
	</style>
	</head>

	<body>
	<div id='map'></div>

	<script>
	var myCenter = new L.LatLng(50.5, 30.51);
	var map = new L.Map('map', { center: myCenter, zoom: 15 });

	var osmCopy = '© <a href="http://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors';
	map.attributionControl.addAttribution(osmCopy);
	var osm = L.tileLayer('http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png');
	var positron = L.tileLayer('https://cartodb-basemaps-{s}.global.ssl.fastly.net/light_all/{z}/{x}/{y}.png', {
	attribution: '© <a href="https://carto.com/attribution">CARTO</a>'
	}).addTo(map);

	var marker = new L.Marker(myCenter);
	map.addLayer(marker);
	marker.bindPopup("<p>Lorem ipsum dolor sit amet</p>");

	L.control.layers({
	'OpenStreetMap Standard': osm,
	'Carto Positron': positron
	}, {
	'Marker': marker
	}
	).addTo(map);


	var layerHashKeys = {
	'osm': osm,
	'positron': positron,
	'marker': marker
	};
	L.myHash(map, layerHashKeys);

	</script>
	</body>

	</html>
	L.MyHash = function(map, options) {
	L.Hash.call(this, map, options);
	};

	L.MyHash.prototype = L.Util.create(L.Hash.prototype);
	L.MyHash.prototype.constructor = L.MyHash;

	L.Util.extend(L.MyHash.prototype, {
	parseHash: function(hash) {
	console.log('parseHash: ' + hash);
	var parsed = L.Hash.prototype.parseHash.call(this, hash);
	console.log('parseHash: ' + JSON.stringify(parsed));
	return parsed;
	},

	formatHash: function(map) {
	var formatted = L.Hash.prototype.formatHash.call(this, map);
	console.log('formatHash: ' + formatted);
	return formatted;
	},

	update: function() {
	L.Hash.prototype.update.call(this);
	console.log('update');
	}
	});

	L.myHash = function(map, options) {
	return new L.MyHash(map, options);
	};