To talk of the Father’s love and becoming children of the Creator God is added: “Dear friends, we are God’s children now” (3:2a), which the author of the letter insists is the case even while admitting that there is a mystery to the purpose of being the children of that God, as he writes “what we will be has not yet been revealed” (3:2b). From here, though confessing that he does not know the precise reason that he and others are have become the children of God or what exactly it will look like when they are functioning as the children of God, he goes on to write that “We know that whenever it (or He) is revealed we will be like Him” (3:2c).
Furthermore, the author goes on to insist that “Jesus was revealed to take away sins” (3:5a). Is it not of the utmost interest that the practice of righteousness (faithfulness to the requirements of the covenant---a right standing) is connected to being fathered by the covenant God and to being His children, with this immediately connected to that which is “revealed”? “Revealed” is used three times in relatively rapid succession before the author makes his grand claim that “the Son of God was revealed: to destroy the works of the devil.” This, of course, is the devil who it has been said has been sinning from the beginning.
So here the term “righteousness” or “covenant faithfulness” is now connected to the children of God. Righteousness is ascribed to Jesus, as the author wants all to know that He is faithful to the covenant. The Son of God, who presumably also operates in righteousness (meeting all covenant requirements), is revealed and sent to destroy the works of the devil, and this seems to be roughly equated, by the author, with being an atoning sacrifice for sins as part of the activity of the love of the Creator God. As has been said, the devil has been operating outside the bounds of the covenant---in covenant unfaithfulness---since the beginning. This, presumably, is what necessitated the revelation of the Son of God, so that such work could be destroyed. This then is the mission of the Son of God.
Inevitably, proper consideration of authorial intent drives one back to the beginning (since the beginning is mentioned), so for the purpose of gaining a more in-depth understanding, one is forced to look to the book of Genesis (the beginning) and to the first revelation of the Son of God. Demonstrating that such is necessary and proper when considering Jesus, it is worth noting in the Gospel of Luke, as the narrative recounts the genealogy of Jesus, traces that lineage back to Adam. In that presentation, Adam is referred to as the son of God. If Adam is the son of God, then he was placed in this world (or revealed) to destroy the works of the devil.
This forces the reader into the realm of cosmology, to look at the beginning of the beginning as far as one with an Israelite worldview is concerned, where one finds that the God of Israel created the heavens and the earth (Genesis 1:1). Somehow and for some reason, without going to deeply into this and thereby getting dramatically off-topic, the earth became “without shape and empty” (1:2), or traditionally, “without form, and void.” The Hebrew words used in this passage, “tohu” and “bohu,” are often taken to imply that this is a new situation far afield from what had been intended by the Creator when He brought the cosmos into existence.