vue/computed-props/index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Computed properties</title>
    <link
      rel="stylesheet"
      href="https://cdnjs.cloudflare.com/ajax/libs/modern-normalize/0.5.0/modern-normalize.min.css"
    />
  </head>
  <body>
    <div id="root">
      <h1>
        {{ reversedMessage }}
      </h1>
      <button @click="showReverse">reverse a message</button>

      <section>
        <h2>My tasks</h2>
        <ul>
          <li v-for="task in tasks" v-text="task.description"></li>
        </ul>
      </section>

      <section>
        <h2>Incomplete tasks</h2>
        <ul>
          <li v-for="task in incompleteTasks" v-text="task.description"></li>
        </ul>
      </section>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/vue@2.6.10/dist/vue.js"></script>
    <script>
      let app = new Vue({
        el: '#root',
        data: {
          message: 'Some message',
          tasks: [
            { description: 'buy ticket', completed: false },
            { description: 'learn JavaScript', completed: false },
            { description: 'invite friends', completed: true },
            { description: 'wait Mom', completed: true },
            { description: 'clean room', completed: false },
            { description: 'sell house', completed: true }
          ]
        },
        computed: {
          reversedMessage() {
            return this.message
              .split('')
              .reverse()
              .join('');
          },
          incompleteTasks() {
            return this.tasks.filter(task => !task.completed);
          }
        },
        methods: {
          showReverse() {
            this.message = this.message
              .split('')
              .reverse()
              .join('');
            return this.message;
          }
        }
      });
    </script>
  </body>
</html>