# Call the JS SDK Methods
source: https://developer.mastercard.com/mastercard-checkout-solutions/tutorial/integrate_sdk/step4/index.md

## Step 4. Call the JS SDK Methods {#step-4-call-the-js-sdk-methods}

The integrator calls [SDK methods](https://developer.mastercard.com/mastercard-checkout-solutions/documentation/sdk-reference/index.md) as needed.

All the Mastercard SDK methods other than the [init()](https://developer.mastercard.com/mastercard-checkout-solutions/documentation/sdk-reference/init/index.md) method use JavaScript promises instead of events/callbacks.
Note: The SDK interprets the backend API calls (as designed) and provides the responses back to the integrator. While XHRs responses can log backend API errors (like 400, INVALID_STATE), integrator should ignore such errors and honor the responses returned by the SDK function calls.