Learning Vue Js with other old version of vue I try to repeat all the steps the same with the new version but the first step doesn't work. :(
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<div id="app">
<h1>{{mensaje}}</h1>
</div>
<!-- version that works -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.4.2/vue.js" ></script>
<!-- version that does not work -->
<!-- <script src="https://cdnjs.cloudflare.com/ajax/libs/vue/3.1.5/vue.cjs.js" ></script> -->
<script>
const app = new Vue({
el:'#app',
data:{
mensaje: 'Hello Vue.js'
}
})
</script>
</body>
</html>