## isEmpty · function

Reactively checks if an observable array, object, Map, or Set is empty.

This function not only returns the current emptiness state but also establishes
a reactive dependency. If the emptiness state of the `proxied` object or array
changes later (e.g., an item is added to an empty array, or the last property
is deleted from an object), the scope that called `isEmpty` will be automatically
scheduled for re-evaluation.

**Signature:** `(proxied: TargetType) => boolean`

**Parameters:**

- `proxied: TargetType` - The observable array, object, Map, or Set to check.

**Returns:** `true` if the array has length 0, the Map/Set has size 0, or the object has no own enumerable properties, `false` otherwise.

**Examples:**

```typescript
const $items = A.proxy([]);

// Reactively display a message if the items array is empty
A('div', () => {
    if (A.isEmpty($items)) {
        A('p i#No items yet!');
    } else {
        A.onEach($items, item => A('p#'+item));
    }
});

// Adding an item will automatically remove the "No items yet!" message
setInterval(() => {
  if (!$items.length || Math.random()>0.5) $items.push('Item');
  else $items.length = 0;
}, 1000)
```