How can I grab a selection of markers with Leaflet.draw?

Context:

I've made a map, and populated it with around 300 random markers. I can 'select' the markers by clicking on a link in the popup and activate a selection to display data from. I also have the Leaflet.draw plugin to draw shapes like circles, rectangles and custom shapes, and I would like to use it to 'select' a couple of markers.

The issue

How can I grab the leaflet marker object of the markers that fall inside a drawn leaflet.draw shape so I can edit them? I cannot seem to make a selection, It either selects none of the markers, or all of them.

Code snippet, stripped from unnecessary code:

const drawControl = new L.Control.Draw({
    draw: {
        marker   : false,
        polygon  : true,
        polyline : false,
        rectangle: true,
        circle   : {
            metric: 'metric'
        }
    },
    edit: false
});

const map = L.map('map', {
    layers: [streets, light]
}).setView([CONFIG.MAP.LATITUDE, CONFIG.MAP.LONGITUDE], CONFIG.MAP.ZOOMLEVEL)

map.addControl(drawControl);

map.on(L.Draw.Event.DRAWSTOP, e => {

    const hello = e.target;

    console.log(hello);
    e.target.eachLayer(layer => {
        if (layer.options.icon) {
            console.log(layer);
        }
    });

});

Most of what you want can quite easily be done using Leaflet's utility methods. If you want to do this with a complex shape like L.Polygon you're going to need something like TurfJS

For L.Circle you need to calculate the distance between the circle's center and compare it to the radius:

var marker = new L.Marker(...),
    circle = new L.Circle(...);

var contains = circle.getLatLng().distanceTo(marker.getLatLng()) < circle.getRadius();

For L.Rectangle you need to fetch it's bounds object and use the contains method:

var marker = new L.Marker(...),
    rectangle = new L.Rectangle(...);

var contains = rectangle.getBounds().contains(marker.getLatLng());

As said for complex polygons i'de use Turf but there are more libraries and plugins out there. Here's an example using Turf's inside method. It take a GeoJSON point and polygon feature as parameters so mind the conversion:

var marker = new L.Marker(...),
    polygon = new L.Polygon(...);

var contains = turf.inside(marker.toGeoJSON(), polygon.toGeoJSON());

You could wrap those into convenience methods for each respective class:

L.Polygon.include({
    contains: function (latLng) {
        return turf.inside(new L.Marker(latLng).toGeoJSON(), this.toGeoJSON());
    } 
});

L.Rectangle.include({
    contains: function (latLng) {
        return this.getBounds().contains(latLng);
    }
});

L.Circle.include({
    contains: function (latLng) {
        return this.getLatLng().distanceTo(latLng) < this.getRadius();
    }
});

var marker = new L.Marker(...),
    polygon = new L.Polygon(...),
    rectangle = new L.Rectangle(...),
    circle = new L.Circle(...);

polygon.contains(marker.getLatLng());
rectangle.contains(marker.getLatLng());
circle.contains(marker.getLatLng());

Note that if you implement the polygon method that there is no need for the rectangle method. Since rectangle is extended from polygon it will inherit the method. I left it in there to be complete.

Now iterating your markers and comparing them is easy:

map.on(L.Draw.Event.CREATED, function (e) {
    markers.eachLayer(function (marker) {
        if (!e.layer.contains(marker.getLatLng())) {
            marker.remove();
        }
    });
});

Hope that helps, here's a working snippet:

var map = new L.Map('leaflet', {
    'center': [0, 0],
    'zoom': 0
});

var markers = new L.LayerGroup().addTo(map);

for (var i = 0; i < 300; i++) {
    var marker = new L.Marker([
        (Math.random() * (90 - -90) + -90).toFixed(5) * 1,
        (Math.random() * (180 - -180) + -180).toFixed(5) * 1
    ]).addTo(markers);
}

new L.Control.Draw({
    draw: {
        marker   : false,
        polygon  : true,
        polyline : false,
        rectangle: true,
        circle   : {
            metric: 'metric'
        }
    },
    edit: false
}).addTo(map);

L.Polygon.include({
    contains: function (latLng) {
        return turf.inside(new L.Marker(latLng).toGeoJSON(), this.toGeoJSON());
    } 
});

L.Rectangle.include({
    contains: function (latLng) {
        return this.getBounds().contains(latLng);
    }
});

L.Circle.include({
    contains: function (latLng) {
        return this.getLatLng().distanceTo(latLng) < this.getRadius();
    }
});

map.on(L.Draw.Event.CREATED, function (e) {
    markers.eachLayer(function (marker) {
        if (!e.layer.contains(marker.getLatLng())) {
            marker.remove();
        }
    });
});

body {
    margin: 0;
}

html, body, #leaflet {
    height: 100%;
}

<!DOCTYPE html>
<html>
  <head>
    <title>Leaflet 1.0.3</title>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <link type="text/css" rel="stylesheet" href="//unpkg.com/leaflet@1.0.3/dist/leaflet.css" />
    <link type="text/css" rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/leaflet.draw/0.4.9/leaflet.draw.css" />
  </head>
  <body>
    <div id="leaflet"></div>
    <script type="application/javascript" src="//unpkg.com/leaflet@1.0.3/dist/leaflet.js"></script>
    <script type="application/javascript" src="//cdnjs.cloudflare.com/ajax/libs/leaflet.draw/0.4.9/leaflet.draw.js"></script>
    <script type="application/javascript" src="//unpkg.com/@turf/turf@latest/turf.min.js"></script>
  </body>
</html>