* Scope CSS selectors with `~` and `+` combinators ([#3104](https://github.com/sveltejs/svelte/issues/3104))
* Fix keyed `{#each}` not reacting to key changing ([#5444](https://github.com/sveltejs/svelte/issues/5444))
* Fix destructuring into store values ([#5449](https://github.com/sveltejs/svelte/issues/5449))
* Fix erroneous `missing-declaration` warning with `use:obj.method` ([#5451](https://github.com/sveltejs/svelte/issues/5451))
## 3.26.0
* Support `use:obj.method` as actions ([#3935](https://github.com/sveltejs/svelte/issues/3935))
* Support `_` as numeric separator ([#5407](https://github.com/sveltejs/svelte/issues/5407))
* Fix assignments to properties on store values ([#5412](https://github.com/sveltejs/svelte/issues/5412))
* Add special style scoping handling of `[open]` selectors on `<details>` elements ([#5421](https://github.com/sveltejs/svelte/issues/5421))
* Support `import.meta` in template expressions ([#5422](https://github.com/sveltejs/svelte/issues/5422))
## 3.25.1
* Fix specificity of certain styles involving a child selector ([#4795](https://github.com/sveltejs/svelte/issues/4795))
* Fix transitions that are parameterised with stores ([#5244](https://github.com/sveltejs/svelte/issues/5244))
* Fix scoping of styles involving child selector and `*` ([#5370](https://github.com/sveltejs/svelte/issues/5370))
* Fix destructuring which reassigns stores ([#5388](https://github.com/sveltejs/svelte/issues/5388))
* Fix `{#await}`s with no `{:catch}` getting stuck unresolved if the promise rejects ([#5401](https://github.com/sveltejs/svelte/issues/5401))
## 3.25.0
* Use `null` rather than `undefined` for coerced bound value of `<input type="number">` ([#1701](https://github.com/sveltejs/svelte/issues/1701))
* Expose object of which slots have received content in `$$slots` ([#2106](https://github.com/sveltejs/svelte/issues/2106))
* Correctly disallow using lifecycle hooks after synchronous component initialisation ([#4259](https://github.com/sveltejs/svelte/issues/4259), [#4899](https://github.com/sveltejs/svelte/issues/4899))
* Re-throw an unhandled rejection when an `{#await}` block with no `{:catch}` gets a rejection ([#5129](https://github.com/sveltejs/svelte/issues/5129))
* Add types to `createEventDispatcher` ([#5211](https://github.com/sveltejs/svelte/issues/5211))
* In SSR mode, do not automatically declare variables for reactive assignments to member expressions ([#5247](https://github.com/sveltejs/svelte/issues/5247))
* Include selector in message of `unused-css-selector` warning ([#5252](https://github.com/sveltejs/svelte/issues/5252))
* Fix using `<Namespaced.Component/>`s in child `{#await}`/`{#each}` contexts ([#5255](https://github.com/sveltejs/svelte/issues/5255))
* Fix using `<svelte:component>` in `{:catch}` ([#5259](https://github.com/sveltejs/svelte/issues/5259))
* Fix setting one-way bound `<input>``value` to `undefined` when it has spread attributes ([#5270](https://github.com/sveltejs/svelte/issues/5270))
* Fix deep two-way bindings inside an `{#each}` involving a store ([#5286](https://github.com/sveltejs/svelte/issues/5286))
* Use valid XHTML for elements that are optimised and inserted with `.innerHTML` ([#5315](https://github.com/sveltejs/svelte/issues/5315))
* Fix reactivity of `$$props` in slot fallback content ([#5367](https://github.com/sveltejs/svelte/issues/5367))
@ -20,6 +20,15 @@ Svelte is a new way to build web applications. It's a compiler that takes your d
Learn more at the [Svelte website](https://svelte.dev), or stop by the [Discord chatroom](https://svelte.dev/chat).
## Supporting Svelte
Svelte is an MIT-licensed open source project with its ongoing development made possible entirely by the support of awesome volunteers. If you'd like to support their efforts, please consider:
- [Becoming a backer on Open Collective](https://opencollective.com/svelte).
Funds donated via Open Collective will be used for compensating expenses related to Svelte's development such as hosting costs. If sufficient donations are received, funds may also be used to support Svelte's development more directly.
## Development
Pull requests are encouraged and always welcome. [Pick an issue](https://github.com/sveltejs/svelte/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc) and help us out!
@ -107,7 +107,7 @@ Your `include`/`exclude` may differ per project — these are defaults that shou
Any editor [using an LSP](https://langserver.org/#implementations-client) can be supported. The [VS Code](https://marketplace.visualstudio.com/items?itemName=svelte.svelte-vscode) extension has been our primary focus, but there is work in progress [on Atom](https://github.com/sveltejs/language-tools/pull/160), and Vim via [coc-svelte](https://github.com/coc-extensions/coc-svelte) has been updated with the latest LSP.
These editor extensions will improve your coding experience even if you only use JavaScript. The editor won't offer errors, but it will offer inference and refactoring tools. You can [add `// @check-js`](https://www.staging-typescript.org/docs/handbook/intro-to-js-ts.html) to the top of a `<script>` tag using JavaScript to get better error messages with no infra changes.
These editor extensions will improve your coding experience even if you only use JavaScript. The editor won't offer errors, but it will offer inference and refactoring tools. You can [add `// @ts-check`](https://www.staging-typescript.org/docs/handbook/intro-to-js-ts.html) to the top of a `<script>` tag using JavaScript to get better error messages with no infra changes.
To switch a `<script>` to use TypeScript, use `<script lang="ts">` and that should be it. Hopefully you won't be seeing an ocean of red squiggles.
@ -107,7 +107,7 @@ An element or component can have multiple spread attributes, interspersed with r
---
*`$$props`* references all props that are passed to a component– including ones that are not declared with `export`. It is useful in rare cases, but not generally recommended, as it is difficult for Svelte to optimise.
*`$$props`* references all props that are passed to a component, including ones that are not declared with `export`. It is not generally recommended, as it is difficult for Svelte to optimise. But it can be useful in rare cases – for example, when you don't know at compile time what props might be passed to a component.
```sv
<Widget{...$$props}/>
@ -115,7 +115,7 @@ An element or component can have multiple spread attributes, interspersed with r
---
*`$$restProps`* contains only the props which are *not* declared with `export`. It can be used to pass down other unknown attributes to an element in a component.
*`$$restProps`* contains only the props which are *not* declared with `export`. It can be used to pass down other unknown attributes to an element in a component. It shares the same optimisation problems as *`$$props`*, and is likewise not recommended.
```html
<input{...$$restProps}>
@ -342,6 +342,33 @@ If you don't care about the pending state, you can also omit the initial block.
{/await}
```
### {#key ...}
```sv
{#key expression}...{/key}
```
Key blocks destroy and recreate their contents when the value of an expression changes.
---
This is useful if you want an element to play its transition whenever a value changes.
```sv
{#key value}
<divtransition:fade>{value}</div>
{/key}
```
---
When used around components, this will cause them to be reinstantiated and reinitialised.
```sv
{#key value}
<Component/>
{/key}
```
### {@html ...}
@ -471,6 +498,7 @@ The following modifiers are available:
* `preventDefault` — calls `event.preventDefault()` before running the handler
* `stopPropagation` — calls `event.stopPropagation()`, preventing the event reaching the next element
* `passive` — improves scrolling performance on touch/wheel events (Svelte will add it automatically where it's safe to do so)
* `nonpassive` — explicitly set `passive: false`
* `capture` — fires the handler during the *capture* phase instead of the *bubbling* phase
* `once` — remove the handler after the first time it runs
* `self` — only trigger handler if event.target is the element itself
@ -13,7 +13,7 @@ First, you'll need to integrate Svelte with a build tool. There are officially m
Don't worry if you're relatively new to web development and haven't used these tools before. We've prepared a simple step-by-step guide, [Svelte for new developers](blog/svelte-for-new-developers), which walks you through the process.
You'll also want to configure your text editor to treat `.svelte` files the same as `.html` for the sake of syntax highlighting. [Read this guide to learn how](blog/setting-up-your-editor).
You'll also want to configure your text editor. If you're using VS Code, install the [Svelte extension](https://marketplace.visualstudio.com/items?itemName=svelte.svelte-vscode), otherwise follow [this guide](blog/setting-up-your-editor) to configure your text editor to treat `.svelte` files the same as `.html` for the sake of syntax highlighting.
Then, once you've got your project set up, using Svelte components is easy. The compiler turns each component into a regular JavaScript class — just import it and instantiate with `new`:
* `preventDefault` — calls `event.preventDefault()` before running the handler. Useful for client-side form handling, for example.
* `stopPropagation` — calls `event.stopPropagation()`, preventing the event reaching the next element
* `passive` — improves scrolling performance on touch/wheel events (Svelte will add it automatically where it's safe to do so)
* `nonpassive` — explicitly set `passive: false`
* `capture` — fires the handler during the *capture* phase instead of the *bubbling* phase ([MDN docs](https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Events#Event_bubbling_and_capture))
* `once` — remove the handler after the first time it runs
* `self` — only trigger handler if event.target is the element itself
Conduitry
5 years ago