{@const ...}

[!NOTE] {@const x = y} is legacy syntax — use {const x = $derived(y)} instead

The {@const ...} tag defines a local constant.

{#each boxes as box}
	{@const area = box.width * box.height}
	{box.width} * {box.height} = {area}
{/each}

{@const} is only allowed as an immediate child of a block — {#if ...}, {#each ...}, {#snippet ...} and so on — a <Component /> or a <svelte:boundary>.