How did the Gospel of John responds to the threat of Gnosticism?

How did the Gospel of John responds to the threat of Gnosticism?

John paid no attention to them.

John rebukes the false teachings. Paul did that too

Asking us to do your homework for you?
Fine, John starts out by saying John 1:1 In the beginning was the Word, and the Word was with God, and the Word was God.
John 1:2 The same was in the beginning with God.
John 1:3 All things were made by him; and without him was not any thing made that was made.

This directly contradicts the Gnostic teaching that the Creator God of the Old Testament is a lesser being called the Demiurge.