Between this and eslint+flycheck I will feel less envious of Visual Studio Code's editor environment (if only there were a way to leverage some of its fantastic IntelliSense from emacs...)
If you're using typescript and emacs, https://github.com/ananthakumaran/tide is a very good integration with the built-in language server for semantic auto-completion and "jump-to" support. I use it every day on large projects.
I think that vscode uses the typescript language server behind-the-scenes for plain javascript analysis.
Tide also works with normal javascript projects. All you need is a jsconfig.json at the root of your project. This gets you the same intellisense as VSC.
I think that vscode uses the typescript language server behind-the-scenes for plain javascript analysis.