# Callbacks

Callbacks are functions that you can provide to a method in the SDK which will give you feedback when an event occurs.

They can be useful when you want to record data & attributes at a particular stage of a transaction.

### sdk.renderCreateTransaction

You can provide a set of callback events to the second parameter of `renderCreateTransaction`.

A list of the supported callbacks are as follows:

| **Callback** | **Description** |
|  --- | --- |
| `onSuccess(transaction)` | Invoked when the transaction, claim (when applicable) & payment is successful. **Warning:** This callback will not be invoked if the user closes the modal before a successful transaction. |
| `onError(error)` | Invoked when an error occurs and the transaction cannot be completed.  **Warning:** This callback will not be invoked if the user closes the modal and the transaction errors afterwards. |
| `onCancel()` | Invoked when the transaction has been cancelled.  **Warning:** This callback will not be invoked if the user closes the modal and the transaction is cancelled afterwards. You can use the [`invoiceCancelled` webhook to track the transaction outcome. |
| `onCloseModal({ transaction, error, status })` | Invoked when the modal has been closed by the user and provides data at the current stage of the transaction.**Example:** it could be possible that the user closes the modal when a claim/payment is pending from the patient. |
| `onTransactionCreated(transaction)` | Invoked when the transaction has been created.**Note:** This does not mean that the transaction is successful yet, there could be a pending claim or payment. |
| `onTransactionUpdated(transaction)` | Invoked when the transaction has been updated.**Note:** A transaction is updated when a claim is created or submitted, or a payment has been made. |


### Example


```js
import medipassSDK from '@medipass/partner-sdk';

medipassSDK.renderCreateTransaction(
  {
    // ... transaction attributes
  },
  {
    onSuccess: function(transaction) {
      console.log(transaction);
      // -> { _id: '123', created: '2022-01-22T23:18:30.329', items: [...], claims: [...], ... }
    },
    onError: function(error) {
      console.log(error);
      // -> { message: 'An error occurred.' }
    },
    onCancel: function() {
      console.log('Transaction cancelled.');
    },
    onCloseModal: function({ transaction, error, status }) {
      if (status === 'success') {
        console.log(transaction);
        // -> { _id: '123', created: '2022-01-22T23:18:30.329', items: [...], claims: [...], ... }
      } else if (status === 'error') {
        console.log(error);
        // -> { message: 'An error occurred.' }
      } else if (status === 'cancelled') {
        console.log('Transaction cancelled.');
      }
    },
    onTransactionCreated: function(transaction) {
      console.log('Transaction created', transaction);
    },
    onTransactionUpdated: function(transaction) {
      console.log('Transaction updated', transaction);
    },
  }
);
```