How to interact with leaflet marker layer from outside the map?

Question

I have a leaflet map showing points for public art pieces, rendered from GeoJSON. Next to the map, I created a list of the pieces from the same GeoJSON data and want to be a

Answer 1

I know this is an older question but Leaflet is on it's way to providing a built-in solution and there is a (somewhat) built-in way to achieve it now...

The approach would be use the layerGroup interface. It provides a method, getLayer, that sounds like it would be perfect get our markers using an ID. However, at this time, Leaflet does not provide any way to specify a custom ID or name.

This issue on Github discusses how this should be done. With that said, you can get and save the auto-generated ID of any Marker (or iLayer for that matter) like so:

let people = [...],
    group = L.layerGroup()

people.forEach(person => {
    let marker = // ... create marker

    group.addLayer( marker );
    person.marker_id = group.getLayerId(marker)
})

Now that we have every marker's ID saved with each backing object in our array of data we can easily get the marker later on like so:

group.getLayer(person.marker_id)

See this pen for a full example and this question for more options...

Answer 2

Felix Kling is right but I'll expand on his comment a little bit...

Since L.LayerGroup and L.FeatureGroup (which L.GeoJSON extends from) don't have methods to retrieve individual layers you will need to either extend from L.GeoJSON and add such a method or keep your own seperate mapping from unique ID to CircleMarker from GeoJSON.

GeoJSON does not require a unique ID but I'll assume that markers in your feed have a unique ID attribute called "id". You will need to add this unique ID to the links that the user can click on so that the links can select the right marker on the map. Then you'll need to store a map of ids to markers in order to retrieve the marker to select it on the map.

markerMap = {}; // a global variable unless you extend L.GeoJSON

// Add the marker id as a data item (called "data-artId") to the "a" element
function addToList(data) {
    for (var i = 0; i < data.features.length; i++) {
        var art = data.features[i];
        $('div#infoContainer').append('<a href="#" class="list-link" data-artId=\"'+art.id+'\" title="' + art.properties.descfin + '"><div class="info-list-item">' + '<div class="info-list-txt">' + '<div class="title">' + art.properties.wrknm + '</div>' + '<br />' + art.properties.location + '</div>' + '<div class="info-list-img">' + art.properties.img_src + '</div>' + '<br />' + '</div></a>')
    }
    $('a.list-link').click(function (e) {
        alert('now you see what happens when you click a list item!');

        //Get the id of the element clicked
        var artId = $(this).data( 'artId' );
        var marker = markerMap[artId];

        //since you're using CircleMarkers the OpenPopup method requires
        //a latlng so I'll just use the center of the circle
        marker.openPopup(marker.getLatLng());
        e.preventDefault()
    })
}

You need to build the markerMap when you get the data from the server. Your pointToLayer method could be modified to do that:

L.geoJson(data, {
    pointToLayer: function (feature, latlng) {
      var marker = new L.CircleMarker( latlng, geojsonMarkerOptions );
      markerMap[feature.id] = marker;
      return marker;
    },...