If you want child wants to communicate back up to the parent, then emit an event from child using $emit object to parent,
Vue.component('todo-item', {
props: ['todo'],
template: `
<div class="todo-item">
<h3>{{ todo.title }}</h3>
<button v-on:click="$emit('increment-count', 1)">
Add
</button>
<div v-html="todo.description"></div>
</div>
`
})
Now you can use this todo-item in parent component to access the count value.
<ul v-for="todo in todos">
<li>
<todo-item
v-bind:key="todo.id"
v-bind:todo="todo"
v-on:increment-count="total += 1"
/></todo-item>
</li>
</ul>
<span> Total todos count is {{total}}</span>
