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docs: add shared state example for bind:group & add labels #14905

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docs: add shared state example for bind:group & add labels #14905

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53 changes: 46 additions & 7 deletions documentation/docs/03-template-syntax/11-bind.md
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Original file line number Diff line number Diff line change
@@ -130,19 +130,58 @@ Inputs that work together can use `bind:group`.
</script>

<!-- grouped radio inputs are mutually exclusive -->
<input type="radio" bind:group={tortilla} value="Plain" />
<input type="radio" bind:group={tortilla} value="Whole wheat" />
<input type="radio" bind:group={tortilla} value="Spinach" />
<label><input type="radio" bind:group={tortilla} value="Plain" />Plain</label>
<label><input type="radio" bind:group={tortilla} value="Whole wheat" />Whole wheat</label>
<label><input type="radio" bind:group={tortilla} value="Spinach" />Spinach</label>

<!-- grouped checkbox inputs populate an array -->
<input type="checkbox" bind:group={fillings} value="Rice" />
<input type="checkbox" bind:group={fillings} value="Beans" />
<input type="checkbox" bind:group={fillings} value="Cheese" />
<input type="checkbox" bind:group={fillings} value="Guac (extra)" />
<label><input type="checkbox" bind:group={fillings} value="Rice" /> Rice</label>
<label><input type="checkbox" bind:group={fillings} value="Beans" />Beans</label>
<label><input type="checkbox" bind:group={fillings} value="Cheese" /> Cheese</label>
<label><input type="checkbox" bind:group={fillings} value="Guac (extra)" />Guac</label>
```

> [!NOTE] `bind:group` only works if the inputs are in the same Svelte component.

`bind:group` can be used with component props with help of [bind-property](#bind:property-for-components):

```javascript
// sharedState.svelte.js
export const tortilla = $state({selectedValue: ""});
export const fillings = $state({selectedValues: []});
```

```svelte
<!-- App.svelte -->
<script>
import { tortilla, fillings } from './sharedState.svelte.js';
import Selection from './Selection.svelte';
</script>

<Selection bind:tortilla={tortilla.selectedValue} bind:fillings={fillings.selectedValues} />
```

```svelte
<!-- Selection.svelte -->
<script>
let { tortilla = $bindable(), fillings = $bindable() } = $props();
</script>

<!-- grouped radio inputs are mutually exclusive -->
<label><input type="radio" bind:group={tortilla} value="Plain" />Plain</label>
<label><input type="radio" bind:group={tortilla} value="Whole wheat" />Whole wheat</label>
<label><input type="radio" bind:group={tortilla} value="Spinach" />Spinach</label>

<!-- grouped checkbox inputs populate an array -->
<label><input type="checkbox" bind:group={fillings} value="Rice" /> Rice</label>
<label><input type="checkbox" bind:group={fillings} value="Beans" />Beans</label>
<label><input type="checkbox" bind:group={fillings} value="Cheese" /> Cheese</label>
<label><input type="checkbox" bind:group={fillings} value="Guac (extra)" />Guac</label>
```

> [!NOTE] `bind:group` only works if the inputs are in the same Svelte component, you can't pass down a single $state to multiple components (with different values).


## `<input bind:files>`

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). When you want to update the files programmatically, you always need to use a `FileList` object. Currently `FileList` objects cannot be constructed directly, so you need to create a new [`DataTransfer`](https://developer.mozilla.org/en-US/docs/Web/API/DataTransfer) object and get `files` from there.