/svelte-core-bestpractices

Keyed each blocks

<!--- copy: false  --->
{#each expression as name (key)}...{/each}

<!--- copy: false  --->
{#each expression as name, index (key)}...{/each}

If a key expression is provided — which must uniquely identify each list item — Svelte will use it to intelligently update the list when data changes by inserting, moving and deleting items, rather than adding or removing items at the end and updating the state in the middle.

The key can be any object, but strings and numbers are recommended since they allow identity to persist when the objects themselves change.

{#each items as item (item.id)}
	<li>{item.name} x {item.qty}</li>
{/each}

<!-- or with additional index value -->
{#each items as item, i (item.id)}
	<li>{i + 1}: {item.name} x {item.qty}</li>
{/each}

You can freely use destructuring and rest patterns in each blocks.

{#each items as { id, name, qty }, i (id)}
	<li>{i + 1}: {name} x {qty}</li>
{/each}

{#each objects as { id, ...rest }}
	<li><span>{id}</span><MyComponent {...rest} /></li>
{/each}

{#each items as [id, ...rest]}
	<li><span>{id}</span><MyComponent values={rest} /></li>
{/each}