Leaflet Slider and Marker Cluster - time not sorted

Question

I use leaflet markercluster along with the ui slider (modified so it can handle a markercluster group as a entry layer, see How to use leaflet slider along with markercluster in Javascript? ).

I managed to make it work except "time" is not sorted in my slider. I don't know what rule SliderControl.js follows to sort the markers but it seems random to me. My data variable (Data_GL) is well time sorted and I specified "timeStrLength: 10" in SliderControl.js.

Here's my code :

var sliderControl = null;

var map = L.map('map').setView([23, 2], 3);
map.options.maxZoom=13;

var osmUrl='http://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png';
var osmAttrib='Map data © OpenStreetMap contributors';
L.tileLayer(osmUrl, {attribution: osmAttrib, id: 'mapbox.streets'}).addTo(map);

var markers = L.markerClusterGroup();
markers.addTo(map);

//Filling layer
var mapdata=Data_GL;

for (var i = 0; i < mapdata.length; i++) {
  var marker = L.marker([mapdata[i].latitude,mapdata[i].longitude],{title: mapdata[i].Platform,icon: cssic0,time: mapdata[i].time});
  marker.bindPopup(mapdata[i].Platform + "<br><b>Type </b>: " + mapdata[i].mtype + "<br><b>Last Update </b>: " + mapdata[i].time);
  console.log(marker.time);
  marker.addTo(markers);};

//Slider
var sliderControl = L.control.sliderControl({layer:markers , range:true});
map.addControl(sliderControl);

sliderControl.startSlider();

Data_GL looks like that :

var Data_GL = [
{"latitude":37.783380,"longitude":15.956680,"mtype":"GL","Platform":"61283","time":"2005-02-21"}, 
{"latitude":37.864970,"longitude":15.826730,"mtype":"GL","Platform":"61282","time":"2005-02-25"}, 
{"latitude":47.639170,"longitude":-8.469670,"mtype":"GL","Platform":"62595","time":"2006-03-12"}, 
{"latitude":59.562670,"longitude":-39.745000,"mtype":"GL","Platform":"64556","time":"2006-08-24"},
...

I tried this solution ( http://jsfiddle.net/nathansnider/ngeLm8c0/4/ ) but I don't really know how to apply it to a markercluster group.

Answer 1

Unfortunately LeafletSlider plugin does not sort layers automatically, even though it does read and show a timestamp.

That is why in the post related to the JSFiddle you mention, the author proposes to sort the input GeoJSON features.

(related post: TimeSlider Plugin and Leaflet - Markers not appearing in order )

But in fact, you should rather sort the options.markers array once you have created the sliderControl , because the order in the GeoJSON can potentially not be followed once it is read by the slider control.

So you would do something like:

var sliderControl = L.control.sliderControl({layer:markers , range:true});

sliderControl.options.markers.sort(function (a, b) {
    return (a.properties.time > b.properties.time);
});

map.addControl(sliderControl);

sliderControl.startSlider();

Note: I updated the first mentioned post with a new method to make LeafletSlider compatible with Leaflet.markercluster. There is no longer need to modify LeafletSlider code, you just use an extra plugin called Leaflet.MarkerCluster.LayerSupport (I am the author).