teststr.re

open Array;

let concatStringArray = (arr : array(string)) : string =>
  fold_left( (acc, item) => acc ++ item, "", arr);

let s = "operation";
let d = None;
let parsingResult = "something I parsed";

Js.log(concatStringArray ([|
    "s:" ++ s ++ ", resulted in ",
    switch d {
    | None => "no date"
    | Some(r) => Js.Date.toISOString(r)
    },
    ", from ",
    parsingResult |])
  );