It's implicitly understood that learning a country's official language(s) is an advantage.
If nothing else you will need to communicate with the authorities constantly - immigration/work permit matters, insurances, health care, etc.
So don't expect English to carry you far unless you know at least the basics of the local language.
And that goes for authorities too. Had a non-Swedish partner for a few years who always communicated in English in all interactions with Sweden's governmental services - no problem. All important government websites are available in English. Knowing Swedish isn't even a requirement for citizenship.
So while knowing Swedish is certainly very beneficial and recommended, you can certainly get by without it, and work for many interesting companies (at least as a developer).
However, all the paperwork you will need to handle will still come in the official language, not in English. All contracts and legal documents will be in that language as well. So not knowing at least the basics will handicap you severely.
I have learned enough of Danish to be able to read the paperwork and do some basic writen communication. That's really the minimum to get you by.
Spoken Danish was a bit too much - the saying that Danish is not a language but a throat disease is not far from the truth!
That said, as soon as I started getting some actual Norwegian language skills, it improved.
(Honestly, though, we probably would've gotten along fine without the translators, as we'd spent a couple months with Rosetta Stone before traveling... we were/are far from fluent, sure, but good enough to order a pizza, I'd imagine ;) ).