.js

{
    console.log('=== body validation')
    const body = {
        uname: 'foo',
        email: 'me@example.com',
        pass1: 'secret',
        pass2: 'secret',
    }
    const v = Validator.succeed(body)
        .andThen(() => {
            return Validator.get('uname', Validator.string()).map(uname => ({
                uname,
            }))
        })
        .andThen(acc => {
            return Validator.get(
                'email',
                Validator.string().andThen(Validator.isEmail)
            ).map(email => ({
                ...acc,
                email,
            }))
        })
        .andThen(acc => {
            return Validator.get('pass1', Validator.string()).map(pass1 => ({
                ...acc,
                pass1,
            }))
        })
        .andThen(acc => {
            return Validator.get(
                'pass2',
                Validator.string().andThen(() => Validator.equalTo(acc.pass1))
            )
                .mapError(() => 'password must match confirmation')
                .map(() => acc)
        })

    console.log(v.apply(body))
}