Cannot use JSX unless the '--jsx' flag is provided. create-react-app code example

Example: Cannot use JSX unless the '--jsx' flag is provided.

// Well I worked around it by adding 
 "jsx": "react" 
// to tsconfig.json, as far as I can tell,
// but that is missing the point.

// When you open a TSX file (not a directory), 
// you don't have a tsconfig.json file.