SpglibJS: C crystal symmetry library transpiled to JavaScript for in-browser usage. See in action online
This is Spglib library ported for the web with LLVM and Emscripten.
Follow the tutorial at the Emscripten website to learn details about transpilation of C source code to JavaScript.
Now to determine crystalline symmetry you need only a browser (without any plugins). This is a pure experiment, and to foster any possible ideas and usecases I created an example web-app (validator.html), providing symmetry validation functionality for CIF or POSCAR files. An explicit symmetry information is absent in POSCARs and often omitted in CIFs, so this web-app provides a quick way of checking the symmetry for such cases. No server is used after page loading, so it is possible to drop a file there and check it without Internet connection (and without any concerns about privacy).
I thank Dr. Atsushi Togo-san for Spglib.
See SpglibJS online.
More info in the blog: https://blog.tilde.pro/handle-crystalline-symmetry-in-browser-using-pure-javascript-6bb01b99d170