Does store-bought salsa have an expiration date/shelf life after being opened?
Like all shelf stable foods, it's fully packed with preservatives... And how long it lasts after being opened, that generally depends on the processing and preservatives in the product.

Being on the safer side, I'd say, even after opening and kept sealed airtight, within 1-2 weeks you should be done with it. But I'm sure, the manufacturer has the right information, written somewhere on the jar...