leave page while still fetching may cause " Failed to fetch " error?

I built a reactjs web with node-fetch, any error catched in the fetch promise will be reported to my server.

Here is the problem : when user fired a fetch request , and left while still waiting for the response , a "Failed to fetch" error will be reported.

So how do I tell if this " Failed to fetch " error is because of the user's early leaving or other reasons? Thank you.