If ESLint reports Uncaught SyntaxError: Unexpected token for an empty line or for a character which does not violate any linting rule, there may be a conflict between multiple ESLint instances.
For example, I received the Unexpected token error for an RxJS Observable which had nothing wrong with it. The reason turned out to be that I had the eslint and babel-eslint libraries running on it, whereas my IDE (VSCode) already used the eslint extension as well.
I opted to disable the native extension in VSCode. The error vanished and linting ran as expected.