<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<div id="vue-instance">
<input type="number" v-model="x">
result: {{ doubleX }}
</div>
<script src="https://cdn.jsdelivr.net/vue/2.1.6/vue.js"></script>
<script>
var vm = new Vue({
el: '#vue-instance',
data: {
x: 1
},
computed: {
doubleX: function(){
return this.x*2;
}
}
});
</script>
</body>
</html>