[SuperZen]

Может посмотреть в сторону легких MVVM?

https://codepen.io/sup3rz3n/pen/jJJzyY

const { h, app } = hyperapp;
/** @jsx h */

const state = {
  form: 0,
  fields: {
    username: '',
    password: '',
    email: ''
  }
};

const actions = {
  changeForm: id => state => ({ form: id }),
  changeField: e => state => ({
    fields: {
      ...state.fields,
      [e.target.name]: e.target.value
    }
  }),
  submit: e => state => {
    e.preventDefault();
    alert(
      `submit ${state.fields.username} ${state.fields.password} ${state.fields.email}`
    )
  }
};

const view = (state, actions) => {
  if (state.form === 0) {
    console.log(state.fields.username)
    return <div>
      <input type="text" name="username" oninput={actions.changeField} value={state.fields.username} />
      <input type="password" name="password" oninput={actions.changeField} value={state.fields.password} />
      <input type="email" name="email" oninput={actions.changeField} value={state.fields.email} />
      <button onclick={() => actions.changeForm(1)} disabled={
        state.fields.username === '' ||
        state.fields.password === '' ||
        state.fields.email === ''
      }>next</button>
    </div>
  } else if (state.form === 1) {
    return <div>form2 {state.fields.username}
      <button onclick={actions.submit}>complete</button>
    </div>
  }
};

const main = app(state, actions, view, document.getElementById('app'));