intersect.js

function convert(lngLatBounds) {
  return {
    topLeft: {
      lng: lngLatBounds.sw.lng,
      lat: lngLatBounds.ne.lat
    },
    bottomRight: {
      lng: lngLatBounds.ne.lng,
      lat: lngLatBounds.sw.lat
    }
  };
}
/**
 * Intersection test for two lat/lng bounding boxes.
 * src: https://rbrundritt.wordpress.com/2009/10/03/determining-if-two-bounding-boxes-overlap/
 * @param  {object} a  Boundingbox 'a'
 * @param  {object} b  Boundingbox 'b'
 * @return {boolean}  True if they intersect
 */
export default function intersect(a, b) {
  const A = convert(a);
  const B = convert(b);

  const Atlx = A.topLeft.lng;
  const Atly = A.topLeft.lat;
  const Abrx = A.bottomRight.lng;
  const Abry = A.bottomRight.lat;

  const Btlx = B.topLeft.lng;
  const Btly = B.topLeft.lat;
  const Bbrx = B.bottomRight.lng;
  const Bbry = B.bottomRight.lat;

  const rABx = Math.abs(Atlx + Abrx - Btlx - Bbrx);
  const rABy = Math.abs(Atly + Abry - Btly - Bbry);

  const rAxBx = Abrx - Atlx + Bbrx - Btlx;
  const rAyBy = Atly - Abry + Btly - Bbry;

  if (rABx <= rAxBx && rABy <= rAyBy) {
    return true;
  }

  return false;
}