How to check if a marker is in a cluster? - leaflet.markercluster

Question

With Leaflet.Markercluster, how is it possible to check if a marker is in a cluster?

Answer 1

Use Leaflet's hasLayer() function
Regular visible markers technically exist as layers in the map. Leaflet also has a function hasLayer() that returns true/false whether a given reference, like a stored marker, currently exists (ie "is visible") in the map as a layer.
For my specific problem, I gave a special visual decoration to a selected map marker (e.g. red border), and this decoration remained even after that marker went in-and-out of a cluster. I needed the selected marker to deselect itself if it entered a cluster.
Below is rough logic that allows me to check whether a given marker reference is visible to the user after a cluster event (that may occur for any reason, like zoom events or non-user driven movements in the map).
Relevant abbreviated code:
I hold my clustering like this...
this.markersClustered = L.markerClusterGroup({ // Lots of stuff here... } })
In my click event for individual markers, I store the marker in a "selectedItem" object (which I use for all kinds of other logic in my app)...
onEachFeature(feature, marker) {
marker.on("click", e => {
// ... (lots of code) ...
// Save instance of the marker; I call it "layer" only
// because I only use this for the hasLayer() check
this.selectedItem.layer = marker
// Here do other stuff too, whatever you need...
//this.selectedItem.target = e.target
//this.selectedItem.latlng = e.latlng
//this.selectedItem.id = e.target.feature.id
//this.selectedItem.icon = layer._icon
// ... (lots of code) ...
})
}
When cluster animations end, using hasLayer(), check whether the selected marker is in a cluster, and do stuff.
Note: the check is done at the END of clustering animation in my use case, because I didn't want the user to see the selected marker lose it's special visual decoration while the clustering animation was happening (it would appear buggy).
this.markersClustered.on('animationend', (e) => {
// Check visibility of selected marker
if(this.map.hasLayer(this.selectedItem.layer)) {
// True: Not in a cluster (ie marker is visible on map)
} else {
// False: In a cluster (ie marker is not visible on map)
}
console.log("Selected marker visible?:" + this.map.hasLayer(this.selectedItem.layer))
})