Fetch API is fine, but Axios[0] gives you a lot more flexibility. The best thing I like is the request/response interceptor. You can do cool stuff like injecting tokens into outgoing requests, retry failed requests, centralized error handling. Because of adapters, it works both in browser environment as well as Node.js environment. Heck, you can even mock requests in your unit tests using a mock adapter[1] to avoid making actual HTTP requests. Sure there is a cost for adding dependency when you can just use native APIs, but in this case, I think it's worth it.
