I really hate the framing here...there are <i>senior devs</i> who <i>use</i> NodeJS.<p>It's not like being a senior dev in language or framework A magically means you're a complete and hopeless noob the second you switch.<p>Sure, you'll have rough patches, but being a good senior dev specifically implies that you know yourself well enough to handle such transitions.
Yes they do. Generally they're not considered senior because they have X years specifically dedicated to Node.js, but instead they have X years of proven development experience with the last 2+ focused on Node.js.
Short answer: Yes<p>Long answer: Yes. There are very senior engineers where JavaScript/Node.js is just one, of many, languages/runtimes that (s)he works with.
It depends on the amount of things and deepness the developer has actually experienced/seen/solved/set up with that particular framework.
I wouldn't assume someone is a senior only based on the years of experience. I've interviewed candidates with 5+ years PHP who are still lacking basic knowledge to be a senior.<p>Start with: what does senior mean for me and my company?