This is code added as a script to a Shopify store with the owner’s permission to change the look and feel of an app installed on that store.
Customized code is typically added directly to one of the files hosted within the theme on your store. On rare occasions, customized code might be hosted outside Shopify, but it still interacts with your theme and your store. Customized code is never added directly to BundleBuilder’s source code.
When customized code is added for BundleBuilder, it usually helps control how bundles look on your store (such as hiding or changing the color of the progress bar), but it can sometimes even alter how bundles function for your customers in minor ways (such as adding buttons to allow your customers to add or subtract variants from a product in a bundle).
The languages used for scripting customized code are typically one or more of HTML, CSS, Liquid (Shopify’s proprietary theme code), or Javascript. This script may interact with the code within your theme, the objects and elements that make up your Shopify store, and/or the parts of the app’s source code that the app’s developers have made available for externally hosted code to interact with.