ESLint not working in VS Code?

If ESLint is running in the terminal but not inside VSCode, it is probably because the extension is unable to detect both the local and the global node_modules folders.

To verify, press Ctrl+Shift+U in VSCode to open the Output panel after opening a JavaScript file with a known eslint issue. If it shows Failed to load the ESLint library for the document {documentName}.js -or- if the Problems tab shows an error or a warning that refers to eslint, then VSCode is having a problem trying to detect the path.

If yes, then set it manually by configuring the eslint.nodePath in the VSCode settings (settings.json). Give it the full path (for example, like "eslint.nodePath": "C:\\Program Files\\nodejs") -- using environment variables is currently not supported.
This option has been documented at the ESLint extension page.

In my case, since I was using TypeScript with React, the fix was simply to tell ESLint to also validate these files. This needs to go in your user settings:

"eslint.validate": [ "javascript", "javascriptreact", "html", "typescriptreact" ],