Template Directives Reference
यह कंटेंट अभी तक आपकी भाषा में उपलब्ध नहीं है।
Template directives are a special kind of HTML attribute available inside of any Astro component template (.astro
files), and some can also be used in .mdx
files.
Template directives are used to control an element or component’s behavior in some way. A template directive could enable some compiler feature that makes your life easier (like using class:list
instead of class
). Or, a directive could tell the Astro compiler to do something special with that component (like hydrating with client:load
).
This page describes all of the template directives available to you in Astro, and how they work.
Rules
Section titled RulesFor a template directive to be valid, it must:
- Include a colon
:
in its name, using the formX:Y
(ex:client:load
). - Be visible to the compiler (ex:
<X {...attr}>
would not work ifattr
contained a directive).
Some template directives, but not all, can take a custom value:
<X client:load />
(takes no value)<X class:list={['some-css-class']} />
(takes an array)
A template directive is never included directly in the final HTML output of a component.
Common Directives
Section titled Common Directivesclass:list
Section titled class:listclass:list={...}
takes an array of class values and converts them into a class string. This is powered by @lukeed’s popular clsx helper library.
class:list
takes an array of several different possible value kinds:
string
: Added to the elementclass
Object
: All truthy keys are added to the elementclass
Array
: flattenedfalse
,null
, orundefined
: skipped
set:html
Section titled set:htmlset:html={string}
injects an HTML string into an element, similar to setting el.innerHTML
.
The value is not automatically escaped by Astro! Be sure that you trust the value, or that you have escaped it manually before passing it to the template. Forgetting to do this will open you up to Cross Site Scripting (XSS) attacks.
You can also use set:html
on a <Fragment>
to avoid adding an unnecessary wrapper element. This can be especially useful when fetching HTML from a CMS.
set:html={Promise<string>}
injects an HTML string into an element that is wrapped in a Promise.
This can be used to inject HTML stored externally, such as in a database.
set:html={Promise<Response>}
injects a Response into an element.
This is most helpful when using fetch()
. For example, fetching old posts from a previous static-site generator.
set:html
can be used on any tag and does not have to include HTML. For example, use with JSON.stringify()
on a <script>
tag to add a JSON-LD schema to your page.
set:text
Section titled set:textset:text={string}
injects a text string into an element, similar to setting el.innerText
. Unlike set:html
, the string
value that is passed is automatically escaped by Astro.
This is equivalent to just passing a variable into a template expression directly (ex: <div>{someText}</div>
) and therefore this directive is not commonly used.
Client Directives
Section titled Client DirectivesThese directives control how UI Framework components are hydrated on the page.
By default, a UI Framework component is not hydrated in the client. If no client:*
directive is provided, its HTML is rendered onto the page without JavaScript.
A client directive can only be used on a UI framework component that is directly imported into a .astro
component. Hydration directives are not supported when using dynamic tags and custom components passed via the components
prop.
client:load
Section titled client:load- Priority: High
- Useful for: Immediately-visible UI elements that need to be interactive as soon as possible.
Load and hydrate the component JavaScript immediately on page load.
client:idle
Section titled client:idle- Priority: Medium
- Useful for: Lower-priority UI elements that don’t need to be immediately interactive.
Load and hydrate the component JavaScript once the page is done with its initial load and the requestIdleCallback
event has fired. If you are in a browser that doesn’t support requestIdleCallback
, then the document load
event is used.
timeout
Section titled timeout
जोड़ा गया:
astro@4.15.0
The maximum time to wait, in milliseconds, before hydrating the component, even if the page is not yet done with its initial load.
This allows you to pass a value for the timeout
option from the requestIdleCallback()
specification. This means you can delay hydration for lower-priority UI elements with more control to ensure your element is interactive within a specified time frame.
client:visible
Section titled client:visible- Priority: Low
- Useful for: Low-priority UI elements that are either far down the page (“below the fold”) or so resource-intensive to load that you would prefer not to load them at all if the user never saw the element.
Load and hydrate the component JavaScript once the component has entered the user’s viewport. This uses an IntersectionObserver
internally to keep track of visibility.
client:visible={{rootMargin}}
Section titled client:visible={{rootMargin}}
जोड़ा गया:
astro@4.1.0
Optionally, a value for rootMargin
can be passed to the underlying IntersectionObserver
. When rootMargin
is specified, the component JavaScript will hydrate when a specified margin (in pixels) around the component enters the viewport, rather than the component itself.
Specifying a rootMargin
value can reduce layout shifts (CLS), allow more time for a component to hydrate on slower internet connections, and make components interactive sooner, enhancing the stability and responsiveness of the page.
client:media
Section titled client:media- Priority: Low
- Useful for: Sidebar toggles, or other elements that might only be visible on certain screen sizes.
client:media={string}
loads and hydrates the component JavaScript once a certain CSS media query is met.
If the component is already hidden and shown by a media query in your CSS, then it can be easier to just use client:visible
and not pass that same media query into the directive.
client:only
Section titled client:onlyclient:only={string}
skips HTML server-rendering, and renders only on the client. It acts similarly to client:load
in that it loads, renders, and hydrates the component immediately on page load.
You must pass the component’s correct framework as a value! Because Astro doesn’t run the component during your build / on the server, Astro doesn’t know what framework your component uses unless you tell it explicitly.
Display loading content
Section titled Display loading contentFor components that render only on the client, it is also possible to display fallback content while they are loading. Use slot="fallback"
on any child element to create content that will be displayed only until your client component is available:
Custom Client Directives
Section titled Custom Client DirectivesSince Astro 2.6.0, integrations can also add custom client:*
directives to change how and when components should be hydrated.
Visit the addClientDirective
API page to learn more about creating a custom client directive.
Script & Style Directives
Section titled Script & Style DirectivesThese directives can only be used on HTML <script>
and <style>
tags, to control how your client-side JavaScript and CSS are handled on the page.
is:global
Section titled is:globalBy default, Astro automatically scopes <style>
CSS rules to the component. You can opt-out of this behavior with the is:global
directive.
is:global
makes the contents of a <style>
tag apply globally on the page when the component is included. This disables Astro’s CSS scoping system. This is equivalent to wrapping all of the selectors within a <style>
tag with :global()
.
You can combine <style>
and <style is:global>
together in the same component, to create some global style rules while still scoping most of your component CSS.
is:inline
Section titled is:inlineBy default, Astro will process, optimize, and bundle any <script>
and <style>
tags that it sees on the page. You can opt-out of this behavior with the is:inline
directive.
is:inline
tells Astro to leave the <script>
or <style>
tag as-is in the final output HTML. The contents will not be processed, optimized, or bundled. This limits some Astro features, like importing an npm package or using a compile-to-CSS language like Sass.
The is:inline
directive means that <style>
and <script>
tags:
- Will not be bundled into an external file. This means that attributes like
defer
which control the loading of an external file will have no effect. - Will not be deduplicated—the element will appear as many times as it is rendered.
- Will not have its
import
/@import
/url()
references resolved relative to the.astro
file. - Will be rendered in the final output HTML exactly where it is authored.
- Styles will be global and not scoped to the component.
The is:inline
directive is implied whenever any attribute other than src
is used on a <script>
or <style>
tag.
The one exception is using the define:vars
directive on the <style>
tag, which does not automatically imply is:inline
.
define:vars
Section titled define:varsdefine:vars={...}
can pass server-side variables from your component frontmatter into the client <script>
or <style>
tags. Any JSON-serializable frontmatter variable is supported, including props
passed to your component through Astro.props
. Values are serialized with JSON.stringify()
.
Using define:vars
on a <script>
tag implies the is:inline
directive, which means your scripts won’t be bundled and will be inlined directly into the HTML.
This is because when Astro bundles a script, it includes and runs the script once even if you include the component containing the script multiple times on one page. define:vars
requires a script to rerun with each set of values, so Astro creates an inline script instead.
For scripts, try passing variables to scripts manually instead.
Advanced Directives
Section titled Advanced Directivesis:raw
Section titled is:rawis:raw
instructs the Astro compiler to treat any children of that element as text. This means that all special Astro templating syntax will be ignored inside of this component.
For example, if you had a custom Katex component that converted some text to HTML, you could have users do this:
Reference