9.cached-computed-properties.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <!-- development version, includes helpful console warnings -->
    <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
    <div id="app">
        <input type="text" v-model="name" />
        <input type="text" id="surname" value="Snow" /><br/>
        <button @click="saveSurname"> Save Surname </button><br/><br/>
        <output>{{computedFullName}}</output>
    </div>
</body>
<script type="text/javascript">
    let surname = 'Snow';
    var app = new Vue({
        el: '#app',
        data: {
            name: 'John',
        },
        computed: {
            computedFullName: function () {
                return this.name + ' ' + surname;
            }
        },
        methods: {
            saveSurname: function(){
                surname = this.$el.querySelector('#surname').value;
            }
        }
    });
</script>
</html>