We are missing some constraints in opam.

js_of_ocaml-toplevel.3.4.0 requires js_of_ocaml-compiler.3.4.0 but you have version 3.3.0 installed.

> [NOTE] Package js_of_ocaml-compiler is already installed (current version is 3.3.0).

try to upgrade your packages

On Thu, May 30, 2019 at 4:28 AM Quaker Quickoats <quakerquickoats@gmail.com> wrote:
okay, not sure, still cannot install js_of_ocaml-toplevel with the same error after opam full update

On Tue, 28 May 2019 at 20:40, Kenichi Asai <asai@is.ocha.ac.jp> wrote:
Thanks for the e-mail.  Yes, you need js_of_ocaml-toplevel and some
other js_of_ocaml packages.  I also installed them with opam 2.0.4:

> js_of_ocaml             3.4.0
> js_of_ocaml-compiler    3.4.0
> js_of_ocaml-ppx         3.4.0
> js_of_ocaml-toplevel    3.4.0

On MacOS, I had no problem installing them...

--
Kenichi Asai