On your own, by yourself.
From cockney rhyming slang, 'Jack Jones = Own'
My friends were busy, so I went to the movies on my J's.
Who wants to go to the museum today?
Not me mate, you're on your J's.
On your own
Oh shit man, dese hench SB brers caught me by my J's an fucked me up.
Being alone
Being by yourself
"We don't like you being on your j's, so we'll just come with you."
to masturbate as a male
Alright guys, I'm gonna go get some lotion and J my D.
You look stressed man, you should go J your D.