A JS port of the venerable geospatial python library Shapely.
Provides both server and client geospatial operations in pure Javascript. ( Will need lots of help to actually pull this one off, so please issue a pull-request )
Why not? After looking at the javascript port of JTS (jsts) you'll realize that (1) it's a very direct port JTS and it depends on OpenLayers. This is fine but its cumbersome. Shapely.js aims to be a bit more intuitive in terms of code and style, and should play nicely with current geojson focused JS libs like leaflet and D3.
Shapely.js is closely following the coding style (a semi-modular pattern) of d3. This is mostly because d3 is great and has a really good pattern for compiling code with uglify js (though it could use grunt.js). This pattern uses a makefile to build the JS code from smaller, more specific "modules". This is super handy for customizing builds.
For testing we're using vows. A popular async capable testing framework that uses node.js to run. Again the pattern follow what @mbostock is doing in d3. To run the tests:
make test