On: Tangle is a JavaScript library for creating reacti...

[xtacy]

While I agree with the comparison, it would be unfair to not point out the wealth of functions that Mathematica exposes:

http://reference.wolfram.com/mathematica/guide/Mathematica.h...

[troymc → xtacy]

Good point! I wonder how much of Mathematica's functionality can be bundled into stand-alone CDF documents (playable by the CDF Player).

Wolfram|Alpha has an API that can be called using JavaScript (for a fee), so some mixed solution is also worth considering.