The JST of John 1:1 reads thusly:
In the beginning was the gospel preached through the Son. And the gospel was the word, and the word was with the Son, and the Son was with God, and the Son was of God.
Most, if not all, Latter-day Saints correctly believe that this is not a textual restoration, but instead, a Midrash-like commentary on John 1:1 and the meaning of the multivalent term translated as "word" (λογος; Hebrew דבר). Indeed, elsewhere in the JST, Jesus is numerically identical to the λογος:
And the same word was made flesh, and dwelt among us, and we beheld his glory, the glory as of the Only Begotten of the Father, full of grace and truth. (John 1:14 JST)
Jesus being one-to-one equivalent with the Word is also explicated in D&C 93:7-8:
And he bore record, saying: I saw his glory, that h was in the beginning, before the world was; therefore, in the beginning the Word was, for he was the word, even the messenger of salvation.
While tentative, perhaps Joseph was influenced by Adam Clarke’s comments about the richness of the meaning of λογος in John 1:1:
Was the Word - Or, existed the Logos. This term should be left untranslated, for the very same reason why the names Jesus and Christ are left untranslated. The first I consider as proper an apellative of the Savior of the world as I do either of the two last. And as it would be highly improper to say, the Deliverer, the Anointed, instead of Jesus Christ, so I deem it improper to say, the Word, instead of the Logos. But as every appellative of the Savior of the world was descriptive of some excellence in his person, nature, or work, so the epithet Λογος, Logos, which signifies a word spoken, speech, eloquence, doctrine, reason, or the faculty of reasoning, is very properly applied to him, who is the true light which lighteth every man who cometh into the world, John 1:9; who is the fountain of all wisdom; who giveth being, life, light, knowledge, and reason, to all men; who is the grand Source of revelation, who has declared God unto mankind; who spake by the prophets, for the testimony of Jesus is the spirit of prophecy, Revelation 19:10; who has illustrated life and immortality by his Gospel, 2 Timothy 1:10; and who has fully made manifest the deep mysteries which lay hidden in the bosom of the invisible God from all eternity, John 1:18.