How to set populate the phone number field on checkout page, from theme extension?

I want to auto populate phone number on checkout page I have a theme extension in which I accept user phone number, I want the same Phone number to be populated when user goes to checkout page. Afaik the cart.js update query doesn’t support updating phone number. Is this possible without using a checkout extension?

Hi Mayank,

Other than a checkout extension, the only option I can think of would be to use the Storefront API’s cartBuyerIdentityUpdate mutation to set the phone number before checkout:


However this may not be feasible with a theme app extension - so you may need to reconsider using a checkout UI extension.