Janvier played for Coach Dameon Jones at perennial power Chaminade-Madonna High School. As a senior, Javier was instrumental in helping Chaminade-Madonna put together a perfect 14-0 season, going 7-0 at home and on the road. Chaminade also captured the state title after competing in their eighth-consecutive title game.
Janvier saw action in eight games and tallied 34 tackles, including 23 solo, including one for a loss, while adding five passes defended, including four interceptions which he returned for 68 yards. As a junior, he was part of a team that captured the state title, with Janvier contributing 34 tackles, six pass breakups, three interceptions and a forced fumble.
The state champion chose FAU over Akron, FIU and Arkansas State.