eithervalidation.ts

import * as E from "fp-ts/Either";
import * as F from "fp-ts/function";

const minxLength = (s: string): E.Either<Error, string> => {
  return s.length < 8 ? E.left(new Error("Password is too short")) : E.right(s);
};
                     
const oneCapital = (s: string): E.Either<Error, string> =>
  /[A-Z]/g.test(s)
    ? E.right(s)
    : E.left(new Error("at least one capital letter"));

const oneNumber = (s: string): E.Either<Error, string> =>
  /[0-9]/g.test(s) ? E.right(s) : E.left(new Error("at least one number"));

// This also works
// F.pipe(minLength(s), E.chain(oneCapital), E.chain(oneNumber));
const validatePassword = (s: string): E.Either<Error, string> =>
  F.pipe(s, minLength, E.chain(oneCapital), E.chain(oneNumber));

// validatePassword('123456'); // Error: at least one capital letter
// validatePassword('salaSANA123'); // salaSANA123