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[docs] Add basic context example #1187

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20 changes: 20 additions & 0 deletions package-lock.json

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1 change: 1 addition & 0 deletions packages/lit-dev-content/package.json
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Expand Up @@ -194,6 +194,7 @@
"slugify": "^1.3.6"
},
"dependencies": {
"@lit-labs/context": "^0.4.1",
"@lit-labs/motion": "^1.0.1",
"@lit-labs/react": "^1.0.8",
"@lit-labs/task": "^3.0.2",
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@@ -0,0 +1,55 @@
import {html, LitElement} from 'lit';
import {customElement, property} from 'lit/decorators.js';
import {provide, consume, createContext} from '@lit-labs/context';

import {providerStyles} from './styles.js';

const contextKey = Symbol('contextKey');
// The values that will be provided and consumed in this demo will
// be strings.
type ContextValue = string;
// Context object, which acts like a key for the context.
// The context object acts as a key. A consumer will only receive
// values from a provider if their contexts match. A Symbol ensures
// that this context will be unique.
const context = createContext<ContextValue>(Symbol());

@customElement('provider-el')
export class ProviderEl extends LitElement {
static styles = providerStyles;

/**
* `data` will be provided to any consumer that is in the DOM tree below it.
*/
@provide({context})
@property()
data = 'Initial';

render() {
return html`
<h3>Provider's data: <code>${this.data}</code></h3>
<slot></slot>
`;
}
}

@customElement('consumer-el')
export class ConsumerEl extends LitElement {
/**
* `providedData` will be populated by the first ancestor element which
* provides a value for `context`.
*/
@consume({context})
providedData = '';

render() {
return html` <h3>Consumer data: <code>${this.providedData}</code></h3> `;
}
}

declare global {
interface HTMLElementTagNameMap {
'provider-el': ProviderEl;
'consumer-el': ConsumerEl;
}
}
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<!DOCTYPE html>
<script type="module" src="./elements.js"></script>
<style>
:root {
font-family: sans-serif;
}
</style>

<h3>Basic Context Example</h3>
<p>
The <code>&lt;consumer-el></code> receives its data from
<code>&lt;provider-el></code> without property drilling.
</p>
<hr>

<provider-el>
<consumer-el></consumer-el>
</provider-el>
<hr>

<provider-el data="specified from attribute">
<consumer-el></consumer-el>
</provider-el>
<hr>

<p>
Checkout our
<a
href="https://lit.dev/docs/data/context/"
target="_blank"
rel="noopener noreferrer"
>Context documentation</a
>!
</p>
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{
"extends": "/samples/base.json",
"title": "Basics",
"description": "Share data from a provider element with Context.",
"section": "@lit-labs/context",
AndrewJakubowicz marked this conversation as resolved.
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"files": {
"elements.ts": {},
"index.html": {},
"styles.ts": {}
},
"package.json": {
"content": "{\n \"dependencies\": {\n \"lit\": \"^2\",\n \"@lit-labs/context\": \"^0.4\"\n}\n}",
"hidden": true
}
}
18 changes: 18 additions & 0 deletions packages/lit-dev-content/samples/examples/context-basics/styles.ts
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import {css} from 'lit';
export const providerStyles = css`
slot {
display: block;
border: dashed 4px #dadada;
padding: 0px 10px;
}

:host {
display: block;
border: solid 4px #adadad;
padding: 2px;
}

h3 {
margin-top: 0;
}
`;
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