Functional input validation

virtual-dom-input-validation.js

// Somewhere

[
  h('input', {
    placeholder: 'card number',
    oninput: function (e) {targets.handleCardNumber({number: e.srcElement.value, state: state})
  }),
  h('span', state.get().cardNumberError)
]

// Elsewhere

function handleCardNumber (stuff) {
  state.set('cardNumber', stuff.number)
  state.set('cardNumberError', getNumberError(stuff.number))
  // maybe set an errors array as well ...
  // maybe disable the submit button as well
}

// Another place

if (paymentObject.errorsArray) {
  // not submitted
}
else {
  submitToken( createToken(paymentObject) )
}

Going to be implementing something like this later today. Structure might end up being a bit different (especially that submit flow) but you get the... gist