Form Fieldset - Bootstrap-Vue

https://bootstrap-vue.github.io/docs/components/form-fieldset

HTML

<link rel="stylesheet" href="https://unpkg.com/bootstrap@next/dist/css/bootstrap.min.css">
<link rel="stylesheet" href="https://unpkg.com/bootstrap-vue@latest/dist/bootstrap-vue.css">
<script src="https://unpkg.com/vue@latest/dist/vue.min.js"></script>
<script src="https://unpkg.com/tether@latest/dist/js/tether.min.js"></script>
<script src="https://unpkg.com/bootstrap-vue@latest/dist/bootstrap-vue.js"></script>
<div id="app">
 

    <b-form-input v-model="name"></b-form-input>
  
 
</div>

CSS

#app {
  padding: 20px;
  height: 300px;
}

JavaScript

new Vue({
  el: '#app',
  computed: {
    feedback() {
      return this.name.length ? '' : 'Please enter something';
    },
    state() {
      return this.name.length ? 'success':'warning';
    },
  },
  data: {
    name: '',
  }
})