By default, the CartStack tracking code will automatically capture any email address that is entered by the website visitor. However, in some cases (eg: the checkout page includes an email field for a gift card recipient in addition to the purchaser's email address), you may only want to capture email addresses for a certain field.
To do this, you can use the setEmailAddressInput. You will just need to include the input field ID value (note: NOT the Name value). All other fields will be ignored.
For example, if this is your input field HTML:
<input type="text" id="billing-email" name="email" />
Your tracking code would look like this: