## NetworksChange event

Triggered when there is a change to the available networks the provided card can run on.
If the list of available networks is still loading, an event with `networks: null` and `loading: true` is triggered.
When the list of available networks loads, Stripe triggers an additional event that contains the list of these networks and shows `loading: false`.
Refer to our [card brand choice guide](/card-brand-choice.md#identifying-the-available-card-networks) for further details.

**Syntax:** `element.on(...)`

#### cardElement

- `event` ('networkschange') **required**
  The name of the event. In this case, `networkschange`.

- `handler` (function) **required**
  `handler(event) => void` is a **callback function** that
you provide that will be called when the event is fired. When called
it will be passed an event object with the following properties:

  - `loading` (boolean)
    `true` if the networks are loading. `false` when Stripe returns all the available networks.

  - `networks` (stringArray | null)
    All available networks for the card number provided. `null` if the networks are still loading.

If eligible for the Card Element's [Card Brand Choice](/card-brand-choice.md) dropdown, this
array will be truncated to a single network so that the user is not presented with multiple
network selections.

### Handle a card networkschange event

```js
cardElement.on('networkschange', function(event) {
  if (event.networks && event.networks.length >= 1) {
    // collect card brand preference
  }
});
```

```es_next
cardElement.on('networkschange', (event) => {
  if (event.networks && event.networks.length >= 1) {
    // collect card brand preference
  }
});
```

#### cardNumberElement

- `event` ('networkschange') **required**
  The name of the event. In this case, `networkschange`.

- `handler` (function) **required**
  `handler(event) => void` is a **callback function** that
you provide that will be called when the event is fired. When called
it will be passed an event object with the following properties:

  - `loading` (boolean)
    `true` if the networks are loading. `false` when Stripe returns all the available networks.

  - `networks` (stringArray | null)
    All available networks for the card number provided. `null` if the networks are still loading.

If eligible for the Card Element's [Card Brand Choice](/card-brand-choice.md) dropdown, this
array will be truncated to a single network so that the user is not presented with multiple
network selections.

### Handle a cardNumber networkschange event

```js
cardNumberElement.on('networkschange', function(event) {
  if (event.networks && event.networks.length >= 1) {
    // collect card brand preference
  }
});
```

```es_next
cardNumberElement.on('networkschange', (event) => {
  if (event.networks && event.networks.length >= 1) {
    // collect card brand preference
  }
});
```