Create scripts by using a Scripts API and the Scripts Library.
What Scripts APIs are available?
Scripts APIs provide the ability to customize the checkout experience for customers:
Payment methods API lets you customize the payment methods that are offered to customers. For example, hide payment methods based on the customer, order, and shipping address, change the order that the payment methods are displayed, and add personalized messages.
Shipping methods API lets you customize the shipping methods offered to customers at checkout. For example, you can hide shipping options, change the order in which they are displayed, and add notes about shipping times. For those familiar with the Scripts Editor, you can't use the Shipping methods API to create shipping discounts. This functionality will be available in upcoming APIs.