window.Vue = require('vue');

Vue.component('example-component', {
    template: '<h2>This is your Vue app</h2>'
});

new Vue({
    el: '#app',
});

<h2>Testing Vue.js component below</h2>
        <div id="app">
              <example-component></example-component>
        </div>

 <script type="text/javascript" src="js/app.js"></script>