Utilizando mutations con composition API:
<template>
<div class="profile">
<div class="box">
<img src="/avatars/avatar.jpg" alt="avatar" />
<label for="username">Nombre de usuario</label>
<input
type="text"
placeholder="Jane Smith"
:value="username"
@input="actualizar($event.target.value)"
/>
<button>Acceder</button>
</div>
</div>
</template>
<script setup>
import { computed } from "vue";
import { useStore } from "vuex";
const store = useStore();
const username = computed(() => store.state.username);
const actualizar = (value) => store.commit("updateUsername", value);
</script>
