1 Nephi 14:27
27. And I, Nephi, heard and bear record, that the name of the apostle of the Lamb was John, according to the word of the angel.
When the Prophet Joseph asked the Lord about some symbolic meanings in the Book of Revelation, he received information about John himself:
14 Q. What are we to understand by the little book that was eaten by John, as mentioned in the 10th chapter of Revelation?
A. We are to understand that it was a mission, and an ordinance, for him to gather the tribes of Israel; behold, this is Elias, who, as it is written, must come and restore all things.
9 Q. What are we to understand by the angel ascending from the east, Revelation 7th chapter and 2nd verse?
A. We are to understand that the angel ascending from the east is he to whom is given the seal of the living God over the twelve tribes of Israel; wherefore, he crieth unto the four angels having the everlasting gospel, saying: Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads. And, if you will receive it, this is Elias that was to come to gather together the tribes of Israel and restore all things (D&C 77:14, 9).
It appears that John is the Elias in both of these verses, and that the book John received (like the book Lehi read) was the account of his own mission, and that his receiving that book was an ordinance that assured his ability to fulfil of that mission. If that is correct, then the Book of Revelation is a brief description of the contents of the book John read—information given to him about what his own mission had been, was then, and would be until after the end when there “should be time no longer” (Revelation 10:6).
John, who was the last living apostle of the meridian of time, was therefore the senior apostle and the last living President of the Church. Since he could not pass on his administrative responsibilities to a successor for almost 2000 years, until Joseph Smith’s time, it appears that John’s mission was to look after things in the interim. Having John be responsible was probably necessary because, even though the whole world was in apostasy, the Lord would not leave the world without the directing hand of mortal (even if translated) men who held the sealing powers of the priesthood. Apparently John was responsible for the things on the European front, that would include bringing Europe through the apostasy and preparing its people for the restoration, while the Three Nephites may have been responsible for doing essentially the same thing in America.