Push_js.pushMessageData
method arrayBuffer : Js_of_ocaml.Typed_array.arrayBuffer Js_of_ocaml.Js.meth
method json : Js_of_ocaml.Js.json Js_of_ocaml.Js.t Js_of_ocaml.Js.meth
method text : Js_of_ocaml.Js.js_string Js_of_ocaml.Js.t Js_of_ocaml.Js.meth