He joined the club from fellow PRO12 side and Champions Cup opponents the Scarlets.
The 20-year-old tight-head prop played for Carmarthen in Wales, before being called up to play for Wales U16s and U18s, which resulted in him joining the Scarlets Academy.
Javan has been at the Scarlets for two years and featured for them in the LV Cup against Sale Sharks last season.
He is Scottish qualified through his father who was born and raised in Edinburgh.
He will play for Ayr when not required by the Warriors.