### Before submitting the PR, please make sure you do the following
- [ ] It's really useful if your PR relates to an outstanding issue, so please reference it in your PR, or create an explanatory one for discussion. In many cases, features are absent for a reason.
- [ ] This message body should clearly illustrate what problems it solves. If there are related issues, remember to reference them.
- [ ] Ideally, include a test that fails without this PR but passes with it. PRs will only be merged once they pass CI. (Remember to `npm run lint`!)
- [ ] It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs
- [ ] This message body should clearly illustrate what problems it solves.
- [ ] Ideally, include a test that fails without this PR but passes with it.
### Tests
- [ ] Run the tests with `npm test`or `yarn test`)
- [ ] Run the tests with `npm test`and lint the project with `npm run lint`
* 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))
## 3.24.1
* Prevent duplicate invalidation with certain two-way component bindings ([#3180](https://github.com/sveltejs/svelte/issues/3180), [#5117](https://github.com/sveltejs/svelte/issues/5117), [#5144](https://github.com/sveltejs/svelte/issues/5144))
* Fix reactivity when passing `$$props` to a `<slot>` ([#3364](https://github.com/sveltejs/svelte/issues/3364))
* Fix transitions on `{#each}``{:else}` ([#4970](https://github.com/sveltejs/svelte/issues/4970))
* Fix unneeded invalidation of `$$props` and `$$restProps` ([#4993](https://github.com/sveltejs/svelte/issues/4993), [#5118](https://github.com/sveltejs/svelte/issues/5118))
* Provide better compiler error message when mismatched tags are due to autoclosing of tags ([#5049](https://github.com/sveltejs/svelte/issues/5049))
@ -43,13 +43,16 @@ When [opening a new issue](https://github.com/sveltejs/svelte/issues/new/choose)
- **One issue, one bug:** Please report a single bug per issue.
- **Provide reproduction steps:** List all the steps necessary to reproduce the issue. The person reading your bug report should be able to follow these steps to reproduce your issue with minimal effort. If possible, use the [REPL](https://svelte.dev/repl) to create your reproduction.
## RFCs
If you'd like to propose an implementation for a large new feature or change then please [create an RFC](https://github.com/sveltejs/rfcs) to discuss it up front.
## Installation
1. Ensure you have [npm](https://www.npmjs.com/get-npm) installed.
1. After cloning the repository, run `npm install` in the root of the repository.
1. To start a development server, run `npm run dev`.
@ -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!
> Quickstart for the impatient: [the Sapper docs](https://sapper.svelte.technology), and the [starter template](https://github.com/sveltejs/sapper-template)
> Quickstart for the impatient: [the Sapper docs](https://sapper.svelte.dev), and the [starter template](https://github.com/sveltejs/sapper-template)
If you had to list the characteristics of the perfect Node.js web application framework, you'd probably come up with something like this:
@ -47,9 +47,9 @@ What happens if we use the new model as a starting point?
## Introducing Sapper
<aside><p>The <ahref="https://sapper.svelte.technology/docs#why-the-name-">name comes from</a> the term for combat engineers, and is also short for Svelte app maker</p></aside>
<aside><p>The <ahref="https://sapper.svelte.dev/docs#Why_the_name">name comes from</a> the term for combat engineers, and is also short for Svelte app maker</p></aside>
[Sapper](https://sapper.svelte.technology) is the answer to that question. **Sapper is a Next.js-style framework that aims to meet the eleven criteria at the top of this article while dramatically reducing the amount of code that gets sent to the browser.** It's implemented as Express-compatible middleware, meaning it's easy to understand and customise.
[Sapper](https://sapper.svelte.dev) is the answer to that question. **Sapper is a Next.js-style framework that aims to meet the eleven criteria at the top of this article while dramatically reducing the amount of code that gets sent to the browser.** It's implemented as Express-compatible middleware, meaning it's easy to understand and customise.
The same 'hello world' app that took 204kb with React and Next weighs just 7kb with Sapper. That number is likely to fall further in the future as we explore the space of optimisation possibilities, such as not shipping any JavaScript *at all* for pages that aren't interactive, beyond the tiny Sapper runtime that handles client-side routing.
@ -51,7 +51,7 @@ Once installed, you'll have access to three new commands:
## Installing a text editor
To write code, you need a good editor. The most popular choice is [Visual Studio Code](https://code.visualstudio.com/) or VSCode, and justifiably so — it's well-designed and fully-featured, and has a wealth of extensions ([including one for Svelte](https://marketplace.visualstudio.com/items?itemName=JamesBirtles.svelte-vscode), which provides syntax highlighting and diagnostic messages when you're writing components).
To write code, you need a good editor. The most popular choice is [Visual Studio Code](https://code.visualstudio.com/) or VSCode, and justifiably so — it's well-designed and fully-featured, and has a wealth of extensions ([including one for Svelte](https://marketplace.visualstudio.com/items?itemName=svelte.svelte-vscode), which provides syntax highlighting and diagnostic messages when you're writing components).
@ -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.
TypeScript support was added to Sapper in 0.28, so if you're using an older version be sure to [upgrade](https://sapper.svelte.dev/migrating#0_27_to_0_28).
@ -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
@ -544,6 +572,21 @@ Numeric input values are coerced; even though `input.value` is a string as far a
<inputtype="range"bind:value={num}>
```
---
On `<input>` elements with `type="file"`, you can use `bind:files` to get the [`FileList` of selected files](https://developer.mozilla.org/en-US/docs/Web/API/FileList).
question: I'm new to Svelte. Where should I start?
---
We think the best way to get started is playing through the interactive [Tutorial](https://svelte.dev/tutorial). Each step there is mainly focused on one specific aspect and is easy to follow. You'll be editing and running real Svelte components right in your browser.
We think the best way to get started is playing through the interactive [Tutorial](tutorial). Each step there is mainly focused on one specific aspect and is easy to follow. You'll be editing and running real Svelte components right in your browser.
Five to ten minutes should be enough to get you up and running. An hour and a half should get you through the entire tutorial.
@ -10,3 +10,11 @@ To declare the type of a reactive variable in a Svelte template, you should use
let x: number;
$: x = count + 1;
```
To import a type or interface make sure to use [TypeScript's `type` modifier](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-8.html#type-only-imports-and-export):
```
import type { SomeInterface } from './SomeFile';
```
You must use the `type` modifier because `svelte-preprocess` doesn't know whether an import is a type or a value — it only transpiles one file at a time without knowledge of the other files and therefore can't safely erase imports which only contain types without this modifier present.
@ -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`:
If you have an object of properties, you can 'spread' them onto a component instead of specifying each one:
If you have an object of properties, you can 'spread' them onto a component instead of specifying each one:
```html
<Info{...pkg}/>
```
> Conversely, if you need to reference all the props that were passed into a component, including ones that weren't declared with `export`, you can do so by accessing `$$props` directly. It's not generally recommended, as it's difficult for Svelte to optimise, but it's useful in rare cases.
> Conversely, if you need to reference all the props that were passed into a component, including ones that weren't declared with `export`, you can do so by accessing `$$props` directly. It's not generally recommended, as it's difficult for Svelte to optimise, but it's useful in rare cases.
* `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
@ -155,7 +157,7 @@ export default class Component {
)||{start: 0,end: 0};
this.warn(svelteOptions,{
code:'custom-element-no-tag',
message:`No custom element 'tag' option was specified. To automatically register a custom element, specify a name with a hyphen in it, e.g. <svelte:options tag="my-thing"/>. To hide this warning, use <svelte:options tag={null}/>`,
message:`No custom element 'tag' option was specified. To automatically register a custom element, specify a name with a hyphen in it, e.g. <svelte:options tag="my-thing"/>. To hide this warning, use <svelte:options tag={null}/>`
Conduitry
5 years ago
