Yes, I think even more so now with the Node Foundation and support for all modern JS syntax (ES6 and beyond). It's being used by mayor players (LinkeIn, Netflix, Medium and Uber to name a few) but also smaller companies (from my personal experience as a freelance developer).
PS Assuming that by web app you mean "the backend for web apps". Otherwise Node would be used 'just' for the build process, together with Webpack and friends.
PS Assuming that by web app you mean "the backend for web apps". Otherwise Node would be used 'just' for the build process, together with Webpack and friends.