<label>
<input type='checkbox' bind:group='selected' value='red'>
red
</label>
<label>
<input type='checkbox' bind:group='selected' value='green'>
green
</label>
<label>
<input type='checkbox' bind:group='selected' value='blue'>
blue
</label>
<p>{selected.join(', ') || 'nothing'} selected</p>
xxxxxxxxxx
{
"selected": ["blue"]
}