Rows.Lookup in SSJS. code example to retrieve row from custom de.
How To Get Variable Value from AMPScritp to SSJS
SFMC comes with default unsubscribe functionality which itself is smart enough to handle critical functionality of unsubscribe procedure, however the challenge here is that we cannot customize its unsubscribe page to give our users personalized and attractive landing page.
Most of the time business wants to use custom profile center instead of vanilla or out of box profile center. Without profile center and physical Email Address you cannot send email. To overcome this scenario you need to add profile center and physical Email Address in Email and hide it using Ampscript.
Most scenarios, it needs to be fetch the data from DE. You can achieve this using SSJS or AMPScript in Salesforce Marketing Cloud.