How to intersect more than 2 polygons using Turf.js?

Question

We use Mapbox GL JS 1.12.0 in our Vue.js project. I need to create intersection objects if I have 2 or more polygons. But, I'm able to do it with 2 polygons only. The code looks as following:

import * as turf from '@turf/turf';

export function createIntersection(features) {
  // features = 3 polygons on the screen bellow
  const intersection = turf.intersect(...features);

  return intersection;
}

The screenshots:

1. Unselected polygons:

2. Selected polygons

3. After code execution

As you can see there is only 1 intersection object created.

How to do it with more than 2 polygons?

Answer 1

turf.intersect() can only intersect 2 polygons.

If you want to intersect multiple polygons you can intersect each polygon with each other polygon with turf.intersect() and then combine the results using turf.combine().

Here is some example code:

const polygonA = ...;
const polygonB = ...;
const polygonC = ...;

const allIntersections = {
  type: 'FeatureCollection',
  features: [
    turf.intersect(polygonA, polygonB),
    turf.intersect(polygonA, polygonC),
    turf.intersect(polygonB, polygonC),
  ],
};

const combinedIntersection = turf.combine(allIntersections);