How can I convert JavaScript values to a variant in reasonml?

Question

There are three values in JavaScript:

• Result.granted
• Result.denied
• Result.neverAskAgain

How can they be converted to a variant?

type result =
    | Granted
    | Denied
    | NeverAskAgain;

Answer 1

Edit: a better option is to use https://bucklescript.github.io/docs/en/generate-converters-accessors#usage-5

You can bind to the values, then write a function which converts the values into a variant.

Bind to the values:

type t';

[@bs.module "result"] external granted: t';
[@bs.module "result"] external denied: t';
[@bs.module "result"] external neverAskAgain: t';

Then convert them into the variant:

type t = Granted | Denied | NeverAskAgain;

let fromJS = t' =>
  switch (t' === granted, t' === denied, t' === neverAskAgain) {
  | (true, _, _) => Granted
  | (_, true, _) => Denied
  | (_, _, true) => NeverAskAgain
  };