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119 lines
4.1 KiB
Markdown
119 lines
4.1 KiB
Markdown
# @astrojs/lit 🔥
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This **[Astro integration][astro-integration]** enables server-side rendering and client-side hydration for your [Lit](https://lit.dev/) custom elements.
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## Installation
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There are two ways to add integrations to your project. Let's try the most convenient option first!
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### `astro add` command
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Astro includes a CLI tool for adding first party integrations: `astro add`. This command will:
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1. (Optionally) Install all necessary dependencies and peer dependencies
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2. (Also optionally) Update your `astro.config.*` file to apply this integration
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To install `@astrojs/lit`, run the following from your project directory and follow the prompts:
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```sh
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# Using NPM
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npx astro add lit
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# Using Yarn
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yarn astro add lit
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# Using PNPM
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pnpx astro add lit
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```
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If you run into any hiccups, [feel free to log an issue on our GitHub](https://github.com/withastro/astro/issues) and try the manual installation steps below.
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### Install dependencies manually
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First, install the `@astrojs/lit` integration like so:
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```sh
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npm install @astrojs/lit
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```
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Most package managers will install associated peer dependencies as well. Still, if you see a "Cannot find package 'lit'" (or similar) warning when you start up Astro, you'll need to install `lit` and `@webcomponents/template-shadowroot`:
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```sh
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npm install lit @webcomponents/template-shadowroot
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```
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Now, apply this integration to your `astro.config.*` file using the `integrations` property:
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__`astro.config.mjs`__
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```js
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import lit from '@astrojs/lit';
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export default {
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// ...
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integrations: [lit()],
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}
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```
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## Getting started
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To use your first Lit component in Astro, head to our [UI framework documentation][astro-ui-frameworks]. This explains:
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- 📦 how framework components are loaded,
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- 💧 client-side hydration options, and
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- 🪆 opportunities to mix and nest frameworks together
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However, there's a key difference with Lit _custom elements_ over conventional _components_: you can use the element tag name directly.
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Astro needs to know which tag is associated with which component script. We expose this through exporting a `tagName` variable from the component script. It looks like this:
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__`src/components/my-element.js`__
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```js
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import { LitElement, html } from 'lit';
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export const tagName = 'my-element';
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class MyElement extends LitElement {
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render() {
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return html` <p>Hello world! From my-element</p> `;
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}
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}
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customElements.define(tagName, MyElement);
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```
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> Note that exporting the `tagName` is __required__ if you want to use the tag name in your templates. Otherwise you can export and use the constructor, like with non custom element frameworks.
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In your Astro template import this component as a side-effect and use the element.
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__`src/pages/index.astro`__
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```astro
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---
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import '../components/my-element.js';
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---
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<my-element></my-element>
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```
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> Note that Lit requires browser globals such as `HTMLElement` and `customElements` to be present. For this reason the Lit renderer shims the server with these globals so Lit can run. You *might* run into libraries that work incorrectly because of this.
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### Polyfills & Hydration
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The renderer automatically handles adding appropriate polyfills for support in browsers that don't have Declarative Shadow DOM. The polyfill is about *1.5kB*. If the browser does support Declarative Shadow DOM then less than 250 bytes are loaded (to feature detect support).
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Hydration is also handled automatically. You can use the same hydration directives such as `client:load`, `client:idle` and `client:visible` as you can with other libraries that Astro supports.
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```astro
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---
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import '../components/my-element.js';
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---
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<my-element client:visible />
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```
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The above will only load the element's JavaScript when the user has scrolled it into view. Since it is server rendered they will not see any jank; it will load and hydrate transparently.
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### More documentation
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Check our [Astro Integration Documentation][astro-integration] for more on integrations.
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[astro-integration]: https://docs.astro.build/en/guides/integrations-guide/
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[astro-ui-frameworks]: https://docs.astro.build/en/core-concepts/framework-components/#using-framework-components
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