> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/sveltejs/svelte/llms.txt
> Use this file to discover all available pages before exploring further.

# SvelteSet

> Reactive Set that triggers updates when modified

The `SvelteSet` class provides a reactive wrapper around JavaScript's `Set`. When you add, delete, or clear items, Svelte's reactivity system is automatically notified.

## Import

```js theme={null}
import { SvelteSet } from 'svelte/reactivity';
```

## Usage

### Basic usage

```svelte theme={null}
<script>
  import { SvelteSet } from 'svelte/reactivity';

  const tags = new SvelteSet(['javascript', 'svelte']);

  function addTag(tag) {
    tags.add(tag);
  }

  function removeTag(tag) {
    tags.delete(tag);
  }
</script>

<ul>
  {#each [...tags] as tag}
    <li>
      {tag}
      <button onclick={() => removeTag(tag)}>×</button>
    </li>
  {/each}
</ul>

<input 
  type="text" 
  onchange={(e) => {
    addTag(e.target.value);
    e.target.value = '';
  }}
/>
```

### Unique selections

```svelte theme={null}
<script>
  import { SvelteSet } from 'svelte/reactivity';

  const selected = new SvelteSet();
  const items = ['Apple', 'Banana', 'Orange', 'Mango'];

  function toggle(item) {
    if (selected.has(item)) {
      selected.delete(item);
    } else {
      selected.add(item);
    }
  }
</script>

<div>
  {#each items as item}
    <label>
      <input
        type="checkbox"
        checked={selected.has(item)}
        onchange={() => toggle(item)}
      />
      {item}
    </label>
  {/each}
</div>

<p>Selected: {selected.size} items</p>
```

## Methods

All standard Set methods work and trigger reactivity when they modify the set:

* `add(value)` - Adds a value
* `delete(value)` - Removes a value
* `clear()` - Removes all values
* `has(value)` - Checks if value exists (doesn't trigger reactivity)
* `size` - Property that returns the number of elements

## Notes

* More efficient than using `$state()` with a regular Set
* Iteration methods work as expected (forEach, keys, values, entries)
* The Set is proxied to track changes automatically

## See also

* [\$state](/runes/state) - General reactive state
* [SvelteMap](/api/reactivity/svelte-map) - Reactive Map
* [SvelteDate](/api/reactivity/svelte-date) - Reactive Date