@turf/union

union

Takes a collection of input polygons and returns a combined polygon. If the input polygons are not contiguous, this function returns a multi-polygon feature.

Parameters

• features FeatureCollection<(Polygon | MultiPolygon)> input polygon features

• options Object Optional Parameters (optional, default {})

  • options.properties GeoJsonProperties properties to assign to output feature (optional, default {})

Examples

const poly1 = turf.polygon(
  [
    [
      [-82.574787, 35.594087],
      [-82.574787, 35.615581],
      [-82.545261, 35.615581],
      [-82.545261, 35.594087],
      [-82.574787, 35.594087],
    ],
  ],
  { fill: "#0f0" }
);

const poly2 = turf.polygon(
  [
    [
      [-82.560024, 35.585153],
      [-82.560024, 35.602602],
      [-82.52964, 35.602602],
      [-82.52964, 35.585153],
      [-82.560024, 35.585153],
    ],
  ],
);

const union = turf.union(turf.featureCollection([poly1, poly2]));

//addToMap
const addToMap = { poly1, poly2, union };

poly1.properties.fill = "#0f0";
poly2.properties.fill = "#00f";
union.properties.stroke = "red";
union.properties["stroke-width"] = 4;
union.properties.fill = "transparent";

Returns (Feature<(Polygon | MultiPolygon)> | null) a combined polygon or multi-polygon feature, or null if there were no input polygons to combine

---

This module is part of the Turfjs project, an open source module collection dedicated to geographic algorithms. It is maintained in the Turfjs/turf repository, where you can create PRs and issues.

Installation

Install this single module individually:

$ npm install @turf/union

Or install the all-encompassing @turf/turf module that includes all modules as functions:

$ npm install @turf/turf