sveltesvelte-store

What is the correct way for updating a Svelte writable array store?

What is the correct way (or differences if both are correct) for updating a $orderItems = writable([]) Svelte writable array store? We'll assume result is a new item I want to push at the end of $orderItems.

orderItems.update(items => ([...items, result]))

or

$orderItems = [...$orderItems, result]
Solution

  • Both are correct and another alternative would be

    $orderItems.push(result)
$orderItems = $orderItems

    and

    orderItems.update(items => {
    items.push(result)
    return items
})

    The difference is that the $ syntax can only be used inside components, so .svelte files. From the docs

    Any time you have a reference to a store, you can access its value inside a component by prefixing it with the $ character. This causes Svelte to declare the prefixed variable, subscribe to the store at component initialization and unsubscribe when appropriate.

    If you want to modify the store from a .js file, this can only be done via .set() / .update()