Since js_of_ocaml cannot transform tail call of function given as an argument into simple loop, event loop with Lwt.bind (>>=) is unimplementable.

actor.ml

let () =
  let n = int_of_string Sys.argv.(1) in
  let open Lwt.Infix in
  let ping = Lwt_mvar.create_empty () in
  let rec consumer () =
    Lwt_mvar.take ping >>= function
    | false -> Lwt.return_unit
    | true -> print_endline "ping"; consumer () in
  let producer () =
    let rec loop i = Lwt_mvar.put ping (i < n) >>= fun () -> loop (i + 1) in
    loop 0 in
  Lwt.async producer;
  Lwt.ignore_result @@ consumer ()

console

bash-3.2$ ocamlfind ocamlc -package lwt -linkpkg -o actor.byte actor.ml && js_of_ocaml actor.byte 
bash-3.2$ ./actor.byte 20000 > /dev/null 
bash-3.2$ node ./actor.js 20000 > /dev/null 
buffer.js:34
    super(arg1, arg2, arg3);
    ^

RangeError: Maximum call stack size exceeded
    at Buffer.Uint8Array (native)
    at FastBuffer (buffer.js:34:5)
    at fromString (buffer.js:274:11)
    at Function.Buffer.from (buffer.js:150:12)
    at decodeChunk (_stream_writable.js:315:20)
    at writeOrBuffer (_stream_writable.js:325:20)
    at SyncWriteStream.Writable.write (_stream_writable.js:274:11)
    at Object.gb [as output] (/Users/koichi/toybox/actor/actor.js:299:77)
    at aw (/Users/koichi/toybox/actor/actor.js:203:40)
    at cy (/Users/koichi/toybox/actor/actor.js:317:88)
    at bd (/Users/koichi/toybox/actor/actor.js:319:29)