How to remove a leaflet label when a topojson layer containing it is removed

Question

I am trying to create an interactive map that visualizes certain data.

I used leaflet map and a topojson layer on it. Next, I tried to add static labels on each of the topojson polygons using leaflet label plugin i.e. the labels should always be there and should not react to mouseover event.

I tried implementing bindLabel() method with noHide:true, but it didn't seem to work. Therefore, I implemented the solution provided to this question Simple label on a leaflet (geojson) polygon . I succeeded in adding static labels.

Then, I have a function that removes a topojson polygon on click event. I was supposed to remove the label on THAT PARTICULAR POLYGON ONLY after it is removed but I cannot seem to implement that.

Here's what I did to add topojson layer and labels:

function addRegions(map) {
    var regionLayer = new L.TopoJSON();
    $.getJSON('region.topo.json').done(addRegionData);

    function addRegionData(topoData) {
        regionLayer.addData(topoData);
        regionLayer.addTo(map);
        regionLayer.eachLayer(addLabel);
        regionLayer.eachLayer(handleLayer);
    }
    function handleLayer(layer) {
        layer.on({
            click: clickAction
        });
    }

// Here's the code for adding label
    function addLabel(layer) {
        var label = new L.Label();  
        label.setContent(layer.feature.properties.REGION);
        label.setLatLng(layer.getBounds().getCenter());
        map.showLabel(label);
    }

// Here's the code that removes a polygon when it is clicked and retains the previously removed polygon
    function clickAction(e) {
        regionLayer.eachLayer(function(layer){
            map.addLayer(layer);
        });
        var layer = e.target;
        map.removeLayer(layer);
    }
}

So far, this code removes the topojson polygon when it is clicked, but the label is still there.

I have to remove the label which is on that particular polygon which is removed, but keep the labels on other polygons.

Also, when the other polygon is clicked, it should be removed but the previously removed label should be retained since the previously removed polygon is also retained.

I cannot, for the life of me think of how to implement that. Please help me.

do the **region** property you're using in as your label is unique for each feature or any other unique property exist in your topojson like **ID**. — muzaffar, Jul 29 '15 at 07:10
The labels don't have any unique id except for their coordinates. I checked at the console, I don't think the labels are associated with any of the topojson property — jimmypage, Jul 29 '15 at 07:37
ofcourse, the labels won't have any topojson property, but the topojson itself do have properties like the **region**, is it unique or any other topojson property is unique? — muzaffar, Jul 29 '15 at 08:02
yes, the topojson does have unique region property... but i dont get it how is it associated with the labels, as i added the labels on the map, not the topojson layer — jimmypage, Jul 29 '15 at 08:05
okay, considering the **region** property is unique, I'm posting a way as an answer. Try that and good luck — muzaffar, Jul 29 '15 at 08:08

score 5 · Accepted Answer · answered Jul 29 '15 at 08:31

Explaination

Firstly, you need to maintain an labels_array where you store your labels so as to remove when required.

Secondly, maintain another unique_property_array where you need to store the unique property you have in your topojson file.

Thirdly, when user would click on any feature, we would get the clicked feature property and match with our unique_property_array, getting the index of the matched value and remove that index from labels_array. Additionally, add the label remove previously.

CodeBlock

Firstly, you need to have three global variables

var labels_array=[];
var unique_property_array=[];
var labelIndexToRemove='';

Secondly, modifiy your addLabel() function this way

function addLabel(layer) {
    var label = new L.Label();  
    label.setContent(layer.feature.properties.REGION);
    label.setLatLng(layer.getBounds().getCenter());
    map.showLabel(label);

    //below two lines are new
    labels_array.push(label);
    unique_property_array.push(layer.feature.properties.region);
}

Lastly, modify your clickAction() function this way

function clickAction(e) {
    regionLayer.eachLayer(function(layer){
        map.addLayer(layer);
    });
    var layer = e.target;
    map.removeLayer(layer);

    //below lines are new
    if(labelIndexToRemove!=''){
        map.addLayer(labels_array[labelIndexToRemove]);
    }
    labelIndexToRemove= unique_property_array.indexOf(e.target.feature.properties.region);
    map.removeLayer(labels_array[labelIndexToRemove]);
}

Try this and tell me if it works. Good luck

How to remove a leaflet label when a topojson layer containing it is removed

1 Answers1

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