You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
svelte/documentation/docs/02-template-syntax/05-styles-and-classes.md

236 lines
5.3 KiB

---
title: Styles & Classes
---
- style scoping
- `:global`
- `style:`
- `class:`
- `--css` props
Styling is a fundamental part of UI components. Svelte helps you style your components with ease, providing useful features out of the box.
## Scoped by default
By default CSS inside a `<style>` block will be scoped to that component.
This works by adding a class to affected elements, which is based on a hash of the component styles (e.g. `svelte-123xyz`).
```svelte
<style>
p {
/* this will only affect <p> elements in this component */
color: burlywood;
}
</style>
```
## :global(...)
To apply styles to a single selector globally, use the `:global(...)` modifier:
```svelte
<style>
:global(body) {
/* applies to <body> */
margin: 0;
}
div :global(strong) {
/* applies to all <strong> elements, in any component,
that are inside <div> elements belonging
to this component */
color: goldenrod;
}
p:global(.big.red) {
/* applies to all <p> elements belonging to this component
with `class="big red"`, even if it is applied
programmatically (for example by a library) */
}
</style>
```
If you want to make @keyframes that are accessible globally, you need to prepend your keyframe names with `-global-`.
The `-global-` part will be removed when compiled, and the keyframe will then be referenced using just `my-animation-name` elsewhere in your code.
```svelte
<style>
@keyframes -global-my-animation-name {
/* code goes here */
}
</style>
```
## :global
To apply styles to a group of selectors globally, create a `:global {...}` block:
```svelte
<style>
:global {
/* applies to every <div> in your application */
div { ... }
/* applies to every <p> in your application */
p { ... }
}
.a :global {
/* applies to every `.b .c .d` element, in any component,
that is inside an `.a` element in this component */
.b .c .d {...}
}
</style>
```
> [!NOTE] The second example above could also be written as an equivalent `.a :global .b .c .d` selector, where everything after the `:global` is unscoped, though the nested form is preferred.
## Nested style tags
There should only be 1 top-level `<style>` tag per component.
However, it is possible to have a `<style>` tag nested inside other elements or logic blocks.
In that case, the `<style>` tag will be inserted as-is into the DOM; no scoping or processing will be done on the `<style>` tag.
```svelte
<div>
<style>
/* this style tag will be inserted as-is */
div {
/* this will apply to all `<div>` elements in the DOM */
color: red;
}
</style>
</div>
```
## class:_name_
```svelte
<!--- copy: false --->
class:name={value}
```
```svelte
<!--- copy: false --->
class:name
```
A `class:` directive provides a shorter way of toggling a class on an element.
```svelte
<!-- These are equivalent -->
<div class={isActive ? 'active' : ''}>...</div>
<div class:active={isActive}>...</div>
<!-- Shorthand, for when name and value match -->
<div class:active>...</div>
<!-- Multiple class toggles can be included -->
<div class:active class:inactive={!active} class:isAdmin>...</div>
```
## style:_property_
```svelte
<!--- copy: false --->
style:property={value}
```
```svelte
<!--- copy: false --->
style:property="value"
```
```svelte
<!--- copy: false --->
style:property
```
The `style:` directive provides a shorthand for setting multiple styles on an element.
```svelte
<!-- These are equivalent -->
<div style:color="red">...</div>
<div style="color: red;">...</div>
<!-- Variables can be used -->
<div style:color={myColor}>...</div>
<!-- Shorthand, for when property and variable name match -->
<div style:color>...</div>
<!-- Multiple styles can be included -->
<div style:color style:width="12rem" style:background-color={darkMode ? 'black' : 'white'}>...</div>
<!-- Styles can be marked as important -->
<div style:color|important="red">...</div>
```
When `style:` directives are combined with `style` attributes, the directives will take precedence:
```svelte
<div style="color: blue;" style:color="red">This will be red</div>
```
## --style-props
```svelte
<!--- copy: false --->
--style-props="anycssvalue"
```
You can also pass styles as props to components for the purposes of theming, using CSS custom properties.
Svelte's implementation is essentially syntactic sugar for adding a wrapper element. This example:
```svelte
<Slider bind:value min={0} --rail-color="black" --track-color="rgb(0, 0, 255)" />
```
Desugars to this:
```svelte
<div style="display: contents; --rail-color: black; --track-color: rgb(0, 0, 255)">
<Slider bind:value min={0} max={100} />
</div>
```
For SVG namespace, the example above desugars into using `<g>` instead:
```svelte
<g style="--rail-color: black; --track-color: rgb(0, 0, 255)">
<Slider bind:value min={0} max={100} />
</g>
```
> [!NOTE] Since this is an extra `<div>` (or `<g>`), beware that your CSS structure might accidentally target this. Be mindful of this added wrapper element when using this feature.
Svelte's CSS Variables support allows for easily themeable components:
```svelte
<style>
.potato-slider-rail {
background-color: var(--rail-color, var(--theme-color, 'purple'));
}
</style>
```
So you can set a high-level theme color:
```css
/* global.css */
html {
--theme-color: black;
}
```
Or override it at the consumer level:
```svelte
<Slider --rail-color="goldenrod" />
```