[GIS] Passing values for a geojson filter in Leaflet

Question

I have a situation where I have a geojson layer in leaflet and I want to create a subset of this layer as a separate geojson to highlight specific features. What I am doing right now is passing in the subset manually as form a separate javascript file (the main feature is loaded as a topojson via omnivore). What I want to be able to, however, is pass the features to be included in the "highlight" geojson as an array of key values (or something similar) so that I can define the features to be included from within the script instead of having to manually pass it in externally.

Answer 1

When you initialize the L.geoJson layer group that you will use as argument of Leaflet Omnivore plugin, you can take advantage of the onEachFeature option to copy a reference of your features into other groups, or even to duplicate your features.

var subGroups = [];

var myGroup = L.geoJson(null, {
  onEachFeature: function (feature, layer) {
    var propValue = feature.properties.prop;
    var subGroup = subGroups[propValue];

    // Initialize the subGroup if it does not exist yet.
    if (!subGroup) {
      subGroup = subGroups[propValue] = L.geoJson();
    }

    // Copy a reference of the layer into the subGroup.
    subGroup.addLayer(layer);
    // You could also create a new layer instead of just a reference.
  }
});

Then when Omnivore converts your file, it will add data into myGroup, and for each added feature, the onEachFeature above function will keep a reference in a "sub group" chosen by the propvalue of the feature.