<script>
	let foo = [];
</script>

<p>Checked: {foo}</p>

<hr>

<input type='checkbox' bind:group={foo} value='a'>a<br>
<input type='checkbox' bind:group={foo} value='b'>b<br>
<input type='checkbox' bind:group={foo} value='c'>c<br>
<input type='checkbox' bind:group={foo} value='d'>d<br>

<hr>

<input type='checkbox' bind:group={foo} value='a'>a<br>
<input type='checkbox' bind:group={foo} value='b'>b<br>
<input type='checkbox' bind:group={foo} value='c'>c<br>
<input type='checkbox' bind:group={foo} value='d'>d<br>