Login security - client side salt - How are people creating this per-user public parameter? -

Login security - client side salt - How are people creating this per-user public parameter? -

because client side salt value should per-user parameter , it's publicly visible on client side (i don't see way hide it), how people determining value should be? i'm not asking how (i.e js library, etc.). know db , salt value has same client side salt coming value? portion of username? value can see beingness consistent between client side , db, i'm not sure. thoughts? help!

security client salt