While compiling lots of misc C/C++ programs into .wasm+.js, I noticed that I can easily run them by just wrapping with code like:

const console = {
  warn: print,
  log: print,
  error: print,
};
function readBinary(p) { return read(p, 'binary'); }

load("mandel.js");

Notice that console.warn and readBinary is enough to run applications generated by emscripten for node.js.

Nice. Presumably none of these programs use threads...