No, I switched from backend programming in ads to backend programming in finance. I did a bit of JS, knew OCaml before, learned Python on the (ads) job, studied math and made programming languages as a hobby so I had a fairly good grasp of a wide range of fundamentals, which basically means I can do pretty much anything you throw at me, in interviews or at the job (anything
ordinary - I don’t have any specialised skills like Google-scale big data or Visa-scale concurrency). I don’t think it would be hard to pick that if you’re really good at JavaScript, I guess curiosity was my strongest feature.
The best thing for getting hired, unfortunately, was my degree (math+finance @ Oxford). Recruiters chased me! I don’t care about the degree, but they do - not necessarily people who interview you, but HR/recruitment department, they use your pedigree to float your CV to the top of the pile
Also interviewing is huge hit and miss. I got rejected by like 5 companies in a row (often initial rounds), then got 2 offers at once (and one of the companies said I was one of the strongest candidates ever).