He who believes? So the NIV is saying that if a person believes, he/she has everlasting life? How do you we know what to believe in to have eternal life? The NIV corrupts this verse by saying "he who believes." Believes on what? The KJV makes it clear by showing us what to believe in by showing us two words. And those two words are "on me." Jesus is making it clear to believe on Him, the Son of the Most High God for everlasting life. The bible says to repent and believe on Jesus for everlasting life in Heaven.
"And this is his commandment, That we should believe on the name of his Son Jesus Christ, and love one another, as he gave us commandment." 1 John 3:23