Vue 3 Composition API

1import { ref, computed, onMounted, watch } from 'vue';
2 
3export default {
4  setup() {
5    const count = ref(0);
6    const message = ref('Hello Vue 3');
7 
8    const doubleCount = computed(() => count.value * 2);
9 
10    const increment = () => {
11      count.value++;
12    };
13 
14    watch(count, (newVal, oldVal) => {
15      console.log(`Count changed: ${oldVal} -> ${newVal}`);
16    });
17 
18    onMounted(() => {
19      console.log('Component mounted');
20    });
21 
22    return {
23      count,
24      message,
25      doubleCount,
26      increment
27    };
28  }
29};