function assert(x) {
  if (!x) throw 'error!';
}

function test() {
  Binaryen.setAPITracing(true);
  var module = new Binaryen.Module();

  module.addCustomSection("hello", [119, 111, 114, 108, 100]);

  assert(module.validate());
  console.log(module.emitText());
}

Binaryen.ready.then(test);