ASP.NET Core with React error - The npm script 'start' exited

Question

I am creating a new asp.net core project in VS 2019. It's a web app in core v5 with React. I have NodeJS v14 installed. When I run the project once I create it, I get this error:

The npm script 'start' exited without indicating that the create-react-app server was listening for requests

I haven't changed any line of code and this is the result of the scaffolding.

Does this answer your question? The NPM script 'start' exited without indicating that the create-react-app server was listening for requests — KennetsuR
– KennetsuR, Commented May 31, 2021 at 5:38
No. The new project scaffolding already has that if condition in place and it's still not working. Plus, it's running in development for me and not working. — Norman W
– Norman W, Commented May 31, 2021 at 6:25
@NormanW - Gonzalo's answer seems to be correct. Worked for me after struggling for weeks with this — brianc
– brianc, Commented Apr 5, 2022 at 19:41

Gonzalo Carmenado · Accepted Answer · 2021-12-10 09:14:46Z

1

Your problem is probably your "ASPNETCORE_ENVIRONMENT" variable in Development enviroment. If you look your Startup.cs file, you will find this lines:

if (env.IsDevelopment())
{
   spa.UseReactDevelopmentServer(npmScript: "start");
}

When you upload that code to a server with the developmen variable, the angular CLI cannot be launched a second time, so it crashes and gives that error message. You can substitute it for:

 #if DEBUG
    spa.UseReactDevelopmentServer(npmScript: "start");
 #endif

I recommend this second option, since if you use the first one, the application will stop working locally.

answered Dec 10, 2021 at 9:14

Gonzalo Carmenado

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