wat.js

const INVALID = 'INVALID';
const VALID = 'VALID';

const Invalid = reasons => ({
  type: INVALID,
  reasons: reasons,
  and: and,
  bifold: bifold
});

const Valid = values => ({
  type: VALID,
  values: values,
  and: and,
  bifold: bifold
});

const and = function(validOrInvalid) {
  //hm, wish there was a tuple
  if (this.type === INVALID) {
    if(validOrInvalid.type === INVALID){
      return Invalid([...this.reasons, ...validOrInvalid.reasons]);
    } else {
      return Invalid(this.reasons);
    }
  } else {
    if(validOrInvalid.type === VALID){
      return Valid([...this.values, ...validOrInvalid.values])
    } else {
      return Invalid(validOrInvalid.reasons)
    }
  }
}

const bifold = function(f, g) {
  if (this.type === INVALID) {
    return f(this.reasons);
  } else {
    return g(this.values);
  }
}

const validateEmail = email => {
  var re = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
  if(re.test(email)){
    return Valid([email]);
  } else {
    return Invalid([`Uh, ${email} didn't match dat regex`]);
  }
}

const assertion1 = validateEmail('[email protected]');
const assertion2 = validateEmail('[email protected]');
const assertion3 = validateEmail('[email protected]');

assertion1.and(assertion2).and(assertion3)
  .bifold(reasons => {
    console.log("We didn't validate..., because:", reasons);
  }, emails => {
    console.log("Yay, we have three emails!", emails);
  })