svelte/test/runtime/samples/binding-input-checkbox-deep-contextual/main.html

{#each items as item}
	<div><input type='checkbox' bind:checked='item.completed'><p>{item.description}</p></div>
{/each}

<p>{numCompleted} completed</p>

<script>
	export default {
		computed: {
			numCompleted ({ items }) {
				return items.reduce( ( total, item ) => total + ( item.completed ? 1 : 0 ), 0 );
			}
		}
	};
</script>