Jesus performed many other signs in the presence of his disciples, which are not recorded in this book. But these are written that you may believe that Jesus is the Messiah, the Son of God, and that by believing you may have life in his name.
John 20:30-31 NIV
Of the four gospel writers, only Luke and John provide us with explicit reasons for their writing. Luke provides an orderly account of what Jesus did in order to give certainty to one who had likely already believed (Luke 1:1-4). John, on the other hand, is more explicitly evangelistic. He writes in order that we might believe, and in believing, have life in Christ.
John is not writing a detailed historical account and is likely not too concerned with getting events in the proper order. John selected seven of Jesus’ signs, or miracles, out of the multitude he had to choose from. He choose those that he felt would be the most useful in leading us to believe. And he concluded with an eighth and greatest sign; the resurrection of Jesus from the dead.
Some people will follow these signs where they lead and will believe, trusting in Christ as their Lord and God. But others will see them and scoff. The choice is yours. Will you see and have faith? Or will you close your eyes and stumble?