@ -205,6 +205,8 @@ In rare cases, you may need to run code _before_ the DOM updates. For this we ca
</div>
```
`$effect.pre` runs before DOM updates that are scheduled after it, not before every DOM mutation in the flush - DOM of parent components may already be updated. When using [await expressions](await-expressions), block updates like `{#if ...}` and `{#each ...}` in the same component also run before `$effect.pre`.
Apart from the timing, `$effect.pre` works exactly like `$effect`.
@ -52,3 +52,5 @@ In this case, you can specify a fallback value for when no prop is passed at all
/// file: FancyInput.svelte
let { value = $bindable('fallback'), ...props } = $props();
```
When a bindable prop has a fallback value, the parent must pass a value other than `undefined` if it uses `bind:`. This avoids ambiguity about which value should apply, since the parent and child should share the same value for a binding.
@ -53,6 +53,12 @@ Transitions can have parameters.
{/if}
```
## Accessibility
Transitions are driven by the [Web Animations API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Animations_API) rather than by CSS. A global `@media (prefers-reduced-motion: reduce)` rule that zeroes `transition-duration` and `animation-duration` therefore has no effect on them.
Use [`prefersReducedMotion`](svelte-motion#prefersReducedMotion) to adjust (or completely disable) the transition accordingly for devices who request reduced motion.
@ -109,7 +109,7 @@ By default, error boundaries have no effect on the server — if an error occurs
Since 5.51 you can control this behaviour for boundaries with a `failed` snippet, by calling [`render(...)`](imperative-component-api#render) with a `transformError` function.
> [!NOTE] If you're using Svelte via a framework such as SvelteKit, you most likely don't have direct access to the `render(...)` call — the framework must configure `transformError` on your behalf. SvelteKit will add support for this in the near future, via the [`handleError`](../kit/hooks#Shared-hooks-handleError) hook.
> [!NOTE] If you're using Svelte via a framework such as SvelteKit, you most likely don't have direct access to the `render(...)` call — the framework must configure `transformError` on your behalf. SvelteKit will add support for this in the near future, via the [`handleError`](../kit/hooks#handleError) hook.
The `transformError` function must return a JSON-stringifiable object which will be used to render the `failed` snippet. This object will be serialized and used to hydrate the snippet in the browser:
@ -102,7 +102,7 @@ To implement a chat window that autoscrolls to the bottom when new messages appe
In Svelte 4, we do this with `beforeUpdate`, but this is a flawed approach — it fires before _every_ update, whether it's relevant or not. In the example below, we need to introduce checks like `updatingMessages` to make sure we don't mess with the scroll position when someone toggles dark mode.
With runes, we can use `$effect.pre`, which behaves the same as `$effect` but runs before the DOM is updated. As long as we explicitly reference `messages` inside the effect body, it will run whenever `messages` changes, but _not_ when `theme` changes.
With runes, we can use `$effect.pre`, which behaves the same as `$effect` but runs before DOM updates scheduled after it (see [$effect.pre]($effect#$effect.pre) for the exact ordering). As long as we explicitly reference `messages` inside the effect body, it will run whenever `messages` changes, but _not_ when `theme` changes.
`beforeUpdate`, and its equally troublesome counterpart `afterUpdate`, are therefore deprecated in Svelte 5.
@ -99,7 +99,9 @@ However, you can use any router library. A sampling of available routers are hig
While most mobile apps are written without using JavaScript, if you'd like to leverage your existing Svelte components and knowledge of Svelte when building mobile apps, you can turn a [SvelteKit SPA](https://kit.svelte.dev/docs/single-page-apps) into a mobile app with [Tauri](https://v2.tauri.app/start/frontend/sveltekit/) or [Capacitor](https://capacitorjs.com/solution/svelte). Mobile features like the camera, geolocation, and push notifications are available via plugins for both platforms.
Some work has been completed towards [custom renderer support in Svelte 5](https://github.com/sveltejs/svelte/issues/15470), but this feature is not yet available. The custom rendering API would support additional mobile frameworks like Lynx JS and Svelte Native. Svelte Native was an option available for Svelte 4, but Svelte 5 does not currently support it. Svelte Native lets you write NativeScript apps using Svelte components that contain [NativeScript UI components](https://docs.nativescript.org/ui/) rather than DOM elements, which may be familiar for users coming from React Native.
You can also write apps in Svelte that compiles to native components by using [Symbiote Native](https://docs.symbiote-native.dev/), which leverages the infrastructure provided by React Native.
Work has been completed towards [custom renderer support in Svelte 5](https://github.com/sveltejs/svelte/issues/15470), but this feature is not yet merged. The custom rendering API will allow support in additional mobile frameworks like Lynx JS and Svelte Native. Symbiote Native will also adopt this API. Svelte Native was an option available for Svelte 4, but Svelte 5 does not currently support it. Svelte Native lets you write NativeScript apps using Svelte components that contain [NativeScript UI components](https://docs.nativescript.org/ui/) rather than DOM elements.
## Can I tell Svelte not to remove my unused styles?
@ -339,27 +339,6 @@ Reactive `$state(...)` proxies and the values they proxy have different identiti
To resolve this, ensure you're comparing values where both values were created with `$state(...)`, or neither were. Note that `$state.raw(...)` will _not_ create a state proxy.
### state_proxy_unmount
```
Tried to unmount a state proxy, rather than a component
```
`unmount` was called with a state proxy:
```js
import { mount, unmount } from 'svelte';
import Component from './Component.svelte';
let target = document.body;
// ---cut---
let component = $state(mount(Component, { target }));
// later...
unmount(component);
```
Avoid using `$state` here. If `component`_does_ need to be reactive for some reason, use `$state.raw` instead.
@ -821,6 +821,18 @@ Cannot use `%rune%` rune in non-runes mode
Cannot use rune without parentheses
```
Runes are keywords rather than values — they can't be assigned to a variable or passed to a function, only called. Referencing one without parentheses is therefore an error...
```js
let count = $state;
```
...whether it's a rune like `$state` or one reached through a property, like `$derived.by`. Add the parentheses, along with any arguments the rune expects:
@ -75,10 +75,10 @@ Certain lifecycle methods can only be used during component initialisation. To f
### missing_context
```
Context was not set in a parent component
Context was not set in the current component or any of its ancestors
```
The [`createContext()`](svelte#createContext) utility returns a `[get, set]` pair of functions. `get` will throw an error if `set` was not used to set the context in a parent component.
The [`createContext()`](svelte#createContext) utility returns a `[get, set]` pair of functions. `get` will throw an error if `set` was not used to set the context in the current component or any of its ancestors.
This module provides a set of functions that allow you to manipulate time values in different ways. It’s particularly useful for animations when combined with the `motion` module.
- fix: preserve CSS escape sequences when printing selectors ([#18667](https://github.com/sveltejs/svelte/pull/18667))
- fix: parse `:nth-child(2n of.foo)` where `of` is not followed by whitespace ([#18611](https://github.com/sveltejs/svelte/pull/18611))
- fix: transform expressions inside labeled statements during server compilation ([#18617](https://github.com/sveltejs/svelte/pull/18617))
- docs: clarify that context lookup includes the current component and all ancestors ([#18581](https://github.com/sveltejs/svelte/pull/18581))
- fix: apply CSS custom properties with falsy values on components ([#18634](https://github.com/sveltejs/svelte/pull/18634))
- fix: correctly print `{#await ... catch x}` et al ([#18645](https://github.com/sveltejs/svelte/pull/18645))
- fix: ignore comments of Program node during migration script ([#18656](https://github.com/sveltejs/svelte/pull/18656))
- fix: reliably resolve append_style to its correct root ([#18614](https://github.com/sveltejs/svelte/pull/18614))
- fix: clean up removed capture event handlers from spread attributes ([#18618](https://github.com/sveltejs/svelte/pull/18618))
- fix: don't corrupt renderer type during SSR's legacy `bind:` retry loop ([#18616](https://github.com/sveltejs/svelte/pull/18616))
- fix: treat concise arrow function bodies as implicit returns when calculating blockers ([#18613](https://github.com/sveltejs/svelte/pull/18613))
- fix: give effect teardowns the value from before the first write in a flush ([#18620](https://github.com/sveltejs/svelte/pull/18620))
- fix: avoid double-calling a derived reference when destructuring `$derived` of another `$derived` during server-side rendering ([#18668](https://github.com/sveltejs/svelte/pull/18668))
- fix: preserve namespaces in CSS type selectors ([#18678](https://github.com/sveltejs/svelte/pull/18678))
- fix: increment private state fields through a non-`this` receiver ([#18622](https://github.com/sveltejs/svelte/pull/18622))
- chore: deduplicate client and server context helpers ([#18580](https://github.com/sveltejs/svelte/pull/18580))
- fix: release `last_propagated_event` after event propagation settles so it no longer retains the last event's target subtree ([#18569](https://github.com/sveltejs/svelte/pull/18569))
- fix: allow custom elements to receive async values as props ([#18661](https://github.com/sveltejs/svelte/pull/18661))
- fix: strip comments from inline `style` values in linear time ([#18553](https://github.com/sveltejs/svelte/pull/18553))
- fix: prevent declaration comments from breaking server derived references ([#18641](https://github.com/sveltejs/svelte/pull/18641))
- perf: make async blocker analysis scale linearly with the number of top-level references ([#18549](https://github.com/sveltejs/svelte/pull/18549))
- fix: preserve short-circuiting for logical assignments to private state fields ([#18594](https://github.com/sveltejs/svelte/pull/18594))
## 5.56.9
### Patch Changes
- fix: skip controlled each fast path while another batch is pending ([#18625](https://github.com/sveltejs/svelte/pull/18625))
@ -295,25 +295,6 @@ To silence the warning, ensure that `value`:
To resolve this, ensure you're comparing values where both values were created with `$state(...)`, or neither were. Note that `$state.raw(...)` will _not_ create a state proxy.
## state_proxy_unmount
> Tried to unmount a state proxy, rather than a component
`unmount` was called with a state proxy:
```js
import { mount, unmount } from 'svelte';
import Component from './Component.svelte';
let target = document.body;
// ---cut---
let component = $state(mount(Component, { target }));
// later...
unmount(component);
```
Avoid using `$state` here. If `component`_does_ need to be reactive for some reason, use `$state.raw` instead.
## svelte_boundary_reset_noop
> A `<svelte:boundary>``reset` function only resets the boundary the first time it is called
@ -186,6 +186,18 @@ This turned out to be buggy and unpredictable, particularly when working with de
> Cannot use rune without parentheses
Runes are keywords rather than values — they can't be assigned to a variable or passed to a function, only called. Referencing one without parentheses is therefore an error...
```js
let count = $state;
```
...whether it's a rune like `$state` or one reached through a property, like `$derived.by`. Add the parentheses, along with any arguments the rune expects:
@ -62,9 +62,9 @@ Certain lifecycle methods can only be used during component initialisation. To f
## missing_context
> Context was not set in a parent component
> Context was not set in the current component or any of its ancestors
The [`createContext()`](svelte#createContext) utility returns a `[get, set]` pair of functions. `get` will throw an error if `set` was not used to set the context in a parent component.
The [`createContext()`](svelte#createContext) utility returns a `[get, set]` pair of functions. `get` will throw an error if `set` was not used to set the context in the current component or any of its ancestors.
@ -247,17 +247,6 @@ export function state_proxy_equality_mismatch(operator) {
}
}
/**
*Triedtounmountastateproxy,ratherthanacomponent
*/
exportfunctionstate_proxy_unmount(){
if(DEV){
console.warn(`%c[svelte] state_proxy_unmount\n%cTried to unmount a state proxy, rather than a component\nhttps://svelte.dev/e/state_proxy_unmount`,bold,normal);
JY Wey
3 weeks ago
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GitHub