Immutable GeoJSON

Immutable.js Record for GeoJSON

This library defines a Immutable.js Record for GeoJSON data. It will handle all the internal nesting of the relevant geometry records, so that it can almost (see Appendix) be used as a drop-in replacement for regular GeoJSON, while maintaining all the goodness of immutable data structures.

Install

npm install immutable-geojson

Usage

import Immutable from 'immutable';
import ImmutableGeoJSON, {Point} from 'immutable-geojson';

const pointA = ImmutableGeoJSON.fromJS({"type": "Point", "coordinates": [100.0, 0.0]});
const type = pointA.type // access to fields via dot syntax thanks to immutable records

const pointB = ImmutableGeoJSON.fromJS({"type": "Point", "coordinates": [100.0, 0.0]});
Immutable.is(pointA, pointB); // true
pointA instanceof Point // true

Caveats

There are two issues that prevent if from being a complete replacement:

Access to coordinates

Since coordinates are arrays in the GeoJSON spec, they are converted to Immutable.Lists. However, immutable lists are not equivalent to arrays. Most notably their fields can't be accesed via bracket syntax (i.e. geometry.coordinates[0]).

However, since Immutable.List implements ES6 iterators, it is possible to access the coordinates via destructuring in ES6:

for (let lineString of geometry.coordinates) {
  for (let [lng, lat] of lineString) {
    // ...
  }
}

Feature properties

Since the structure of the properties field of GeoJSON Features can't be known in advance, it uses a generic Immutable.Map to store the values as an Immutable.Collection (so that comparisons via Immutable.is don't depend on identical references).

If you want to use records for the properties as well, you can provide a reviver as second parameter to fromJS (similar to fromJS in Immutable.js)