As contractions the difference between wouldja and wouldna
is that wouldja is eye dialect of would you while wouldna is contraction of would not have|lang=en.
wouldja
English
Contraction
(
en-cont)
* 2002 , Erich Segal, Love Story , HarperCollins, page 47:
- She screwed up her brow and frowned. "Oh Oliver, wouldja please?"
wouldna
English
Contraction
(
en-cont)
(colloquial)
- I wouldna done that if I were you.
See also
* coulda
* shouldna
* woulda
* wouldn't've