Do I need a Janome walking foot?
 

Or can I buy the Singer brand one they sell at JAF's and it fit my 2122?

It should be fine, I have a janome and a singer and I have Distinctive brand walking feet on both of them.

I have a Singer walking foot for my Janome 2212 and it attaches fine but doesn't work very well, no matter what stitch length I set it on I get teeny tiny stitches, like it doesn't feed properly. I'd had another (non-Janome) foot that worked just fine but something broke inside after just a few uses and Amazon was kind enough to replace it with the Singer but I guess I should have gone with another brand.

Usually a brand-specific walking foot will work better than a generic (or other brand). Personally, I would pay extra for a Janome walking foot designed for that specific machine (or group of machines).

I have both a singer and a janome and they are interchangeable on my machine. I can't tell a difference. But for some reason I do use each one with it's named foot.

Thanks all for the information. I am currently making my first ever anything on my Janome so I will stick to the JAF walking foot. If I see myself un the future using my machine more than A few times a year I will invest in a better Janome brand one.

Side note, I was watching a Youtube video on walking foots and the presenter said that walking foots cannot stitch backwards. Is this true?

Walking feet can stitch backwards (at least all of the ones I have ever owned). However, I believe it isn't recommended to do it excessively. It must be hard on the mechanism. It is also recommended not to operate a walking foot on high speeds.

I have 2 generic walking feet. They both fit on all 3 of my Janome machines and work just fine. Also if you want to sew in reverse drop your needle, turn you project around, stitch as far as you need to, drop the needle again, turn the project around and you have backstitched as desired. I don't want to use my walking foot to stitch in reverse in case it does hurt the foot. Even the generic feet are not cheap.
Sue

Not all walking feet can stitch backwards, but I'm not sure which can and which cannot.