TURF
A modular geospatial engine written in JavaScript
...It includes traditional spatial operations, helper functions for creating GeoJSON data, and data classification and statistics tools. Turf can be added to your website as a client-side plugin, or you can run Turf server-side with Node.js. Modular, simple-to-understand JavaScript functions that speak GeoJSON. Turf is a collection of small modules, you only need to take what you want to use. Takes advantage of the newest algorithms and doesn't require you to send data to a server. TypeScript definitions are packaged with each module. No DefinitelyTyped packages required. ...