There are quite a lot of ways to say yes or something like it in Swedish. Almost all of them are a more informal way of saying it though. Synonyms for "Ja" just det (that's right), javisst (sure), visst (sure), japp (yes, informal), jadå (yes, informal), det är riktigt (that's right), jaja (yes, yes), jaha (often said if surprised or despondent), okej, OK, jajamensan (yes, sure), jodå (yeah), instämmer (I agree), självklart (naturally), yes, jo (sure), jojomen (yeah, sure), jomen, jo men visst (sure I can do that/I can agree to that), jajamän (that's right, informal), alldeles så (that's right), naturligtvis (naturally) There are many more as well. We tend to change our way of saying yes as just saying "ja" can be boring haha.

one of the more useful variations of "ja" is "jo", which is used to disagree with a negatively constructed sentence. if you're familiar with german, "doch" operates in the same way in that language. so one way you might see it is like this: "du har inte en lägenhet, eller hur?" "jo, den har jag." "you don't have an apartment, do you?" "yes, i do."