If any of you actually need such constraint satisfaction in javascript, checkout my fd.js library [1]. You'll find einstein, sudoku and other puzzles in the tests.js file.

I also recommend a Mozart/Oz style interactive search tree explorer made by a student [2] .. built on fd.js.

[1] https://github.com/srikumarks/fd.js [2] http://minhtule.github.io/Search-Tree-Visualization/