We have a good clue as to where the entry point is from our examination of the Startup class in the ASP.NET Core backend. In the Configure method, the SPA middleware is set up with the source path as ClientApp:

app.UseSpa(spa =>
{
  spa.Options.SourcePath = "ClientApp";

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

If we look in the ClientApp folder, we'll see a file called package.json. This is a file that is often used in React apps and contains information about the project, its npm dependencies, and the scripts that can be run to perform tasks. 

If we open the package.json file, we will see react listed as a dependency:

"dependencies": {
  "react": "^16.0.0",
  "react-scripts": "^3.0.1",
  ...
},

So, we are definitely in the right place! The react-scripts dependency gives us a big clue as to how exactly React was scaffolded. react-scripts  is a set of scripts from the popular Create React App (CRA) tool that was built by the developers at Facebook. This tool has done a huge amount of configuration for us, including a development server, bundling, linting, and unit testing. We'll learn more about CRA in the next chapter.

The root HTML page for an app scaffolded by CRA is index.html, which can be found in the public folder in the ClientApp folder. It is this page that hosts the React app. The root JavaScript file that is executed for an app scaffolded by CRA is index.js, which is in the ClientApp folder. We'll examine both the index.html and index.js files later in this chapter.