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# Method name: count()

# Method package: wixData

# Method menu location: wixData --> WixDataAggregate --> count

# Method Link: https://dev.wix.com/docs/velo/apis/wix-data/wix-data-aggregate/count.md

# Method Description:

Refines a `WixDataAggregate` to contain the item count of each group in the aggregation.

The `count()` function refines a `WixDataAggregate` to contain the item
 count in each of the aggregate's groups.

 When the aggregation is [run](#run), the returned `WixDataAggregateResult`
 object contains items with the following additional `key:value` pair:

 + The key is named `"count"`.
 + The value is the count of items aggregated in the group.


 > **Note:** Aggregations can only be used on collections you have created. They cannot be
 used on [Wix App Collections](https://support.wix.com/en/article/cms-formerly-content-manager-working-with-wix-app-collections).



# Method Code Examples:

*** Note: do not assume any prop names or enum values other than the ones in the example.

## Add a sum aggregation

```javascript
let newAggregate = aggregate.count();
```

## Create an aggregation, add a sum aggregation, and run it

```javascript
import wixData from 'wix-data';

// ...

wixData.aggregate("PopulationData")
  .group("state", "year")
  .count()
  .run()
  .then((results) => {
    if (results.items.length > 0) {
      let items = results.items;        // see below
      let numItems = results.length;    // 6
      let hasNext = results.hasNext();  // false
    } else {
      // handle case where no matching items found
    }
  })
  .catch((error) => {
    let errorMsg = error.message;
    let code = error.code;
  });

/* Given the sample data above, items is:
 * [
 *   {
 *     "_id": {"state": "NY", "year": 2000},
 *     "count": 2,
 *     "state": "NY",
 *     "year": 2000
 *   },
 *   {
 *     "_id": {"state": "FL", "year": 2000},
 *     "count": 2,
 *     "state": "FL",
 *     "year": 2000
 *   },
 *   {
 *     "_id": {"state": "CA", "year": 2000},
 *     "count": 2,
 *     "state": "CA",
 *     "year": 2000
 *   },
 *   {
 *     "_id": {"state": "FL", "year": 2010},
 *     "count": 2,
 *     "state": "FL",
 *     "year": 2010
 *   },
 *   {
 *     "_id": {"state": "CA", "year": 2010},
 *     "count": 2,
 *     "state": "CA",
 *     "year": 2010
 *   },
 *   {
 *     "_id": {"state": "NY", "year": 2010},
 *     "count": 2,
 *     "state": "NY",
 *     "year": 2010
 *   }
 * ]
 */
```

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