GEOS.js

(WIP) GEOS.js is an easy-to-use geospatial library built on top of GEOS.

The goal of this library is to connect turf-like ease of use with the reliability of GEOS (used by PostGIS, QGIS, GDAL, Shapely and many others).

Try it out

Try out GEOS.js in the interactive playground!

You can also check out API Documentation for live examples!

Project structure

At the core is the C/C++ GEOS library compiled by Emscripten into WebAssembly. Memory management, pointers and other C/C++/Wasm related stuff are handled by JavaScript wrapper, which by exposing a clean API almost makes Wasm an implementation detail for downstream developers.

GEOS.js custom GeoJSON integration offers fast and efficient way to transfer data between JavaScript and Wasm memory. It also has some unique capabilities like:

• support for feature ID and properties
• support for Z and M ordinates
• support for geometries that are not part of the official GeoJSON format: CircularString, CompoundCurve, CurvePolygon etc.

Install

npm i geos.js

Quick start

import { initializeFromBase64, fromWKT, toWKT, toWKB, point, area, buffer, union } from 'geos.js';

// GEOS.js needs to be initialized (to compile Wasm code)
await initializeFromBase64();

// GEOS.js can read and write GeoJSON, WKT and WKB
const p1 = buffer(fromWKT('POINT (1 1)'), 10);
const p2 = buffer(point([ 6, 6 ]), 8, { quadrantSegments: 2 });
const u = union(p1, p2);

console.log(area(u)); // 375.3168319264665
console.log(toWKT(u, { precision: 1 })); // 'POLYGON ((10.8 -1, 10.2 -2.8, 9.3 -4.6, 8.1 -6.1, 6...
console.log(u.toJSON()); // { type: 'Feature', geometry: { type: 'Polygon', coordinates: [ [ 10....
console.log(JSON.stringify(u)); // '{"type":"Feature","geometry":{"type":"Polygon","coordinates"...

console.log(toWKB(fromWKT('POINT Z (1 2 3)'), { flavor: 'iso' })); // Uint8Array(29) [1,233,3,0,...

Bundle size

The main components of the library are a Wasm file and a JavaScript wrapper.

They can be combined into a single .js file where .wasm file data is embedded as Base64 string:

| file | size | gzipped | |----------------|--------:|--------:| | index.min.js | 1400 KB | 469 KB |

or loaded separately:

| file | size | gzipped | |---------------------|--------:|--------:| | geos_js.wasm | 1033 KB | 327 KB | | index-slim.min.js | 24 KB | 7 KB |

index-slim here is a complete JavaScript wrapper, but without initializeFromBase64 function.

License

GEOS.js is licensed under MIT License. GEOS is available under the terms of GNU Lesser General Public License (LGPL) 2.1.

Related Projects

• The inspiration for this library was the geos-wasm library created by Christoph Pahmeyer
• Turf - pure JavaScript library with similar functionality
• Shapely - Python package build on top of GEOS