Here's how I'd build a simple form

login.js

var Struct = require('observ-struct')
var Email = require('email-input')
var Password = require('password-input') // doesn't actually exist yet
var value = require('observ-value')
var h = require('virtual-dom/h')
var when = require('value-when')

function LoginForm (data) {
  data = data || {}
  
  return State({
    email: Email(data.email),
    password: Password(data.password)
  })
}

LoginForm.valid = valid
function valid (state) {
  state = value(state)
  return state.email.valid && state.password.valid
}

LoginForm.render = function render (state) {
  return h('form', [
    Email.render(state.email),
    Password.render(state.email),
    h('button', {
      type: 'submit',
      attributes: {
        disabled: when(valid(state), '')
      }
    })
  ])
}