svelte/documentation/tutorial/06-bindings/03-checkbox-inputs/app-b/App.svelte

<script>
	let yes = false;
</script>

<label>
	<input type="checkbox" bind:checked={yes} />
	Yes! Send me regular email spam
</label>

{#if yes}
	<p>Thank you. We will bombard your inbox and sell your personal details.</p>
{:else}
	<p>You must opt-in to continue. If you're not paying, you're the product.</p>
{/if}

<button disabled={!yes}> Subscribe </button>