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 able to click on an item from the list outside of the map and have the related marker's popup come up on the map.

How can I link the list of items to their respective markers through a click event?

My map.js file looks like this:

var map;
var pointsLayer;

$(document).ready(function () {
    map = new L.Map('mapContainer');
    var url = 'http://{s}.tiles.mapbox.com/v3/mapbox.mapbox-streets/{z}/{x}/{y}.png';
    var copyright = 'Map data © 2011 OpenStreetMap contributors, Imagery © 2011 CloudMade';
    var tileLayer = new L.TileLayer(url, {
        attribution: copyright
    });
    var startPosition = new L.LatLng(41.883333, - 87.633333);
    map.on('load', function (e) {
        requestUpdatedPoints(e.target.getBounds())
    });
    map.setView(startPosition, 13).addLayer(tileLayer);
    map.on('moveend', function (e) {
        requestUpdatedPoints(e.target.getBounds())
    })
});

function requestUpdatedPoints(bounds) {
    $.ajax({
        type: 'GET',
        url: '/SeeAll',
        dataType: 'json',
        data: JSON.stringify(bounds),
        contentType: 'application/json; charset=utf-8',
        success: function (result) {
            parseNewPoints(result);
            addToList(result)
        },
        error: function (req, status, error) {
            alert('what happen? did you lose conn. to server ?')
        }
    })
}

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" 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!');
        e.preventDefault()
    })
}

function parseNewPoints(data) {
    if (pointsLayer != undefined) {
        map.removeLayer(pointsLayer)
    }
    pointsLayer = new L.GeoJSON();
    var geojsonMarkerOptions = {
        radius: 8,
        fillColor: "#FF6788",
        color: "YELLOW",
        weight: 1,
        opacity: 1,
        fillOpacity: 0.5
    };
    L.geoJson(data, {
        pointToLayer: function (feature, latlng) {
            return L.circleMarker(latlng, geojsonMarkerOptions)
        },
        onEachFeature: function (feature, pointsLayer) {
            pointsLayer.bindPopup(feature.properties.img_src + "<br />" + feature.properties.wrknm + "<br />" + feature.properties.artist + "<br />" + feature.properties.location + '<div class="description">' + feature.properties.descfin + '</div>')
        }
    }).addTo(map)
}

Answer 1

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;
    },...