Does Any Data Layer Exist For 3Rd Party Integration

Store Builder Questions
1

Hi All,

Is there any data layer which exists in the MVE which can be accessed by third party systems to fetch info as user info, product added to cart , etc. ?

Thx

2

What about REST API?

http://docs.cs-cart.com/4.3.x/developer_guide/api/index.html

3

actually we need to run some javascript code on press of Buy button which will pass the value of product to the javascript for further processing