Attempt to type https://github.com/mui-org/material-ui/blob/3e4854b39b17511d9b312071ca93061eeb503f5d/packages/material-ui/src/styles/createBreakpoints.js

Breakpoints.re

type breakpoint = [ | `lg | `md | `sm | `xl | `xs ];

type breakpointsObj = {
  .
  "keys": array(string),
  "values": {
    .
    "lg": int,
    "md": int,
    "sm": int,
    "xl": int,
    "xs": int,
  },
  /* "unit": string, */
};

[@bs.module "material-ui/styles/createBreakpoints"]
external create : Js.t({..}) => breakpointsObj = "default";

let value = (bo: breakpointsObj, k: breakpoint) =>
  switch (k) {
  | `lg => bo##values##lg
  | `md => bo##values##md
  | `sm => bo##values##sm
  | `xl => bo##values##xl
  | `xs => bo##values##xs
  };

let defaultBreakpoints = create(Js.Obj.empty());

let minWidth = (value, _unit) =>
  "(min-width:" ++ string_of_int(value) ++ _unit ++ ")";

let maxWidth = (value, _unit) =>
  "(max-width:" ++ string_of_int(value) ++ _unit ++ ")";

let up = (bo: breakpointsObj, k: breakpoint) => {
  minWidth(value(bo, k), "px"); /* How to acess unit property ? bo##unit is invalid*/
};

let upDefault = up(defaultBreakpoints);