{@const ...}

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>.