It's one thing to have an application that works; it's another to have an application that works and has maintainable code that doesn't make people's eyes bleed. The best way to achieve measurable code quality is to adopt a standard, like Airbnb's (https://github.com/airbnb/javascript). The best way to enforce coding standards is to use a linter. With React applications, the preferred linting tool is ESLint (https://eslint.org/).