I took jq's C code and compiled it with Emscripten, then added a wrapper so it would run on a browser with either asm.js or WebAssembly.
I believe I needed it for requesthub.xyz but I'm not sure I ever used it there. I also intended to use it on another (secret) project that relied on heavy data manipulation on the client, but it turned out to be too slow for that so I opted to use JavaScript directly. Later I used it for a client-side Etleneum simulator, but removed it later as it was impossible to replicate most of the Etleneum functionality on the client so the simulator was too broken and confusing.