Stophface

{"type":"FeatureCollection","features":[{"type":"Feature","geometry":{"type":"MultiPolygon","coordinates":[[[[102,2],[103,2],[103,3],[102,3],[102,2]]],[[[100,0],[101,0],[101,1],[100,1],[100,0]],[[100.2,0.2],[100.2,0.8],[100.8,0.8],[100.8,0.2],[100.2,0.2]]],[[[100.3,0.3],[100.7,0.3],[100.7,0.7],[100.3,0.7],[100.3,0.3]],[[100.4305160192801,0.67817296142852],[100.43926588878527,0.6777431305923907],[100.44793148784716,0.6764577778174132],[100.45642935778174,0.6743292824257617],[100.46467765559704,0.6713781440787653],[100.47259694234847,0.667632785305691],[100.48011094831709,0.6631292777150927],[100.48714730763562,0.6579109945286341],[100.49363825528266,0.6520281927874464],[100.49952127973005,0.6455375292587178],[100.50473972495757,0.6385015147088778],[100.50924333603814,0.6309879118031904],[100.5129887430422,0.6230690824341719],[100.51593987860606,0.6148212907677792],[100.51806832514795,0.6063239687221135],[100.51935358839506,0.5976589509544159],[100.51978329459449,0.5889096867249723],[100.51935330951578,0.580160

Stophface

// Turf union can be very slow 
// The part that is slowing down turf.union() is, that the union function has to compare all the coordinates with each other, in order to avoid duplicate coordinates
// We can speed up this process in two ways
// 1) Only compare the coordinates of the polygons that intersect (idea of ChatGPT)
// 2) Pairwise combine the polygons recursively The cost of computing the union of two polygons scales with the number of points in each. So you can reduce the runtime by reducing the number of operations that involve large polygons. (idea of https://stackoverflow.com/a/70010562/3935035) 

const findIntersectingPolygons = (geojson) => {
  const allPolygons = turf.getCoords(geojson);
  const bboxes = allPolygons.map((coords, index) => {
    const polygon = turf.polygon(coords);

Stophface

Stophface