[GIS] turf js union with array of features

geojsonmapbox-gl-jsturf

I am using Mapbox GL JS and querying a source on a common ID. 

var tempId= 55;

var relatedFeatures=map.querySourceFeatures('featureSource', {
    sourceLayer: "sourceLayerId",
    filter: ['in', "FID",tempId]
 });

This returns an array of geojson features. If I pass this directly to turf union like below it throws an error

turf.union(relatedFeatures)

I can iterate over the array like below and union the features together but this seems unnecessary. Any suggestion for doing this more efficiently?

var featuresJoined=relatedFeatures[1]
  if(relatedFeatures.length>1){
    $.each(relatedFeatures,function(i,item){
      if(i>1){
        featuresJoined=turf.union(featuresJoined,item)                      
      }
    })
  }

Best Answer

Your approach of iterating over each feature is a valid approach.

According to http://turfjs.org/docs/#union union doesn't accept an array of features instead each feature must be an argument to union, so if you're targeting ES6 you can use spread syntax.

turf.union(...relatedFeatures)

Otherwise Magnus's answer should also work.

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