Typed Functional Programming in TypeScript with fp-ts

import * as t from ‘io-ts’; const Email = t.brand( t.string, (s): s is t.Branded<string, EmailBrand> => isEmail(s), ‘Email’, ); type Email = t.TypeOf<typeof Email>;

Email.decode(”) Email.decode(‘r0b1n’) Email.decode(‘r@0b1n.at’) Email.decode(2020) Email.decode(null)

import * as E from ‘fp-ts/lib/Either’ pipe( Email.decode(anything), E.fold(onFail, onSuccess) )

const a: Email = ‘r@0b1n.at’ // -> Type ‘“r@0b1n.at”’ is not assignable to type ‘Branded<string, Email>’.

const SignUpForm = t.type({ company: String50, email: Email, password: Password, phone: option(Phone), sendNewsletter: t.boolean, }); const form = useForm( SignUpForm, initialState );

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