I am making custom app for product option . How to do selected all option then calculate total price product and update total price on cart json?
for example : https://apps.shopify.com/product-options
these already apply this method.
Any one can let me know How its work?
Your question isn't clear but I'll take a bit of a guess at what you need.
The price of a cart is controlled by the variants it contains. If you're hoping to add value to a cart you either need to pick a more expensive variant, or add in other variants to increase it. An example of this would be for monogramming. The base product is added and to capture a monogramming fee another product is added at the same time.