asm.js
Strict subset of JavaScript optimized for AOT compilation. Mozilla, 2013. Type annotations via codes (x|0 = int, +x = double). Precursor to WebAssembly.
Pitch: compile C/C++ to asm.js via Emscripten → runs near-native speed in the browser. Demo: Epic Citadel (Unreal Engine 3) ran in the browser in 2013. Browsers (all except Edge initially) added specific optimization. asm.js → WebAssembly evolution: same team, same idea, but binary format instead of JS subset. WebAssembly (2017) made asm.js redundant. Lives only in historical benchmarks + some Mozilla demos.