JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://vuejs.org/js/vue.min.js"></script>
<div id="demo">    
    <input type="number" min=0 v-on:input="change">
    <p>{{num}}</p>
    
    <button  v-on:click="saveFaculties" class="btn btn-primary">
     Registrar
    </button>
    
</div>

JavaScript

var data = {
    num:0
}

var demo = new Vue({
    el: '#demo',
    data: data,
  methods: {
    saveFaculties(){
                    console.log("Registrando.");
                    this.num = 3;
                },
  	change: function(event) {
    	console.log(event.target.value);
      this.num = event.target.value;
    }
  }
})