PatrickJS/environment.config.json

## environment.config.json
{
    "environment": "staging"
}

## index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <script>
      (async () => {
        // The chunks required to get this application up and running in an
        // isolated context.
        const isolationChunks = [
          "main", // The bundle that initialises the application.
          "remoteEntry" // This applications remoteEntry file.
        ];

        // The chunks that point to the `remoteEntry,js` files for the other
        // federated modules associated with the applicationthat will create
        // the graph in conjunction with the `isolatedChunks`.
        const remoteChunks = [
          "appOne",
          "appTwo",
          "utilities"
        ];

        // References to the endpoints that we need to get the configuration files
        // from to initialise the application again the current session.
        const configChunks = [
          "http://example.com/location.config.json", // Global location config.
          "../environment.config.json" // Per environment config.
        ];

        // Grab our configuration files in parallel.
        const [location, { environment }] = await Promise.all(
          configChunks.map(chunk => fetch(chunk).then(response => response.json()))
        );

        // Reference our configuration files against the global window so that
        // our dynamic `publicPath` function can grab them when initialising our
        // bundles.
        window.__ENVIRONMENT__ = environment;
        window.__LOCATION__ = location;

        // Now that we have our configuration, lets get the javascript we need to
        // initialise the application. We parallelise the requests to keep things
        // speedy.
        await Promise.all([
            // Fetch the `remoteEntry.js` files for our federated dependancies.
            ...remoteChunks
              .map(chunk => {
                const { href } = location[chunk][environment];
                return fetch(`${href}/remoteEntry.js`).then(response => response.text());
              }),
            // Get files dedicated to running this micro front-end in isolation
            // mode.
            ...isolationChunks
              .map(chunk => fetch(`./${chunk}.js`)
                .then(response => response.text())
              )
          ])
          .then(scripts => scripts.forEach(script => {
              // Now that we have our scripts, let's inject them onto the page
              // so that we can run out application initialisation sequence.
              const element = document.createElement("script");
              element.text = script;
              document.querySelector("body").appendChild(element);
          }));
      })();
    </script>
  </head>
  <body></body>
</html>

## location.config.json
{
    "shell": {
        "development": {
            "href": "http://localhost:8000/"
        },
        "staging": {
            "href": "http://staging.shell.example.com/"
        },
        "production": {
            "href": "http://prod.shell.example.com/"
        }
    },
    "appOne": {
        "development": {
            "href": "http://localhost:8001/"
        },
        "staging": {
            "href": "http://staging.app-one.example.com/"
        },
        "production": {
            "href": "http://prod.app-one.example.com/"
        }
    },
    "appTwo": {
        "development": {
            "href": "http://localhost:8002/"
        },
        "staging": {
            "href": "http://staging.app-two.example.com/"
        },
        "production": {
            "href": "http://prod.app-two.example.com/"
        }
    },
    "utilities": {
        "development": {
            "href": "http://localhost:8003/"
        },
        "staging": {
            "href": "http://staging.utilities.example.com/"
        },
        "production": {
            "href": "http://prod.utilities.example.com/"
        }
    }
}

## webpack.config.js
...

/**
 * Allows static builds to change their `publicName` dynamically at run time rather
 * than build time. This allows builds to be environment agnostic, where we can
 * change from Staging, UAT, to Production with the same artefact and have the
 * `publicName` update accordingly via some run time configuration.
 * @class
 */
class DynamicPublicPathPlugin {
  /**
   * The Webpack hook to apply our plugin.
   * @parem {Object} compiler - The Webpack compiler.
  */
  apply(compiler) {

    compiler.hooks.make.tap("MutateRuntime", (compilation) => {

      compilation.hooks.runtimeModule.tap("MutateRuntime", (module, chunk) => {

        const isPublicPathRuntimeModule = module.constructor.name === "PublicPathRuntimeModule";

        if (!isPublicPathRuntimeModule) { return; }

        console.log(`* Update "${chunk.name}" dynamic public path`);

        // We extract the variable "key" (the namespace to left of the equals sign)
        // and leave the rest behind as we are going to build our own new value
        // and assign it back to the variable.
        const [key] = module.getGeneratedCode().split("=");

        // Swap out the old static string value for a function that will run in
        // the browser session and create a public path based on the current
        // configuration.
        //
        // We create the `publicPath` from the "environment.config.json" and
        // "location.config.json" configuration files that are saved as global
        // variables in the browser `__ENVIRONEMENT__` and `__LOCATION__`.
        module._cachedGeneratedCode = `${key}=(function() {
          const { __LOCATION__,  __ENVIRONEMENT__ } = window;
          const { href } = __LOCATION__.shell[__ENVIRONEMENT__];
          const publicPath = href + "/";

          return publicPath;
        })();`

        return module;

      });
    });
  }
}

...

module.exports = async (_, args) => {
  ...

  return {
    ...

    plugins: [
      new ModuleFederationPlugin({
        ...
      }),

      new DynamicPublicPathPlugin(),

      ...

    ]

    ...
};
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<script>
	(async () => {
	// The chunks required to get this application up and running in an
	// isolated context.
	const isolationChunks = [
	"main", // The bundle that initialises the application.
	"remoteEntry" // This applications remoteEntry file.
	];

	// The chunks that point to the `remoteEntry,js` files for the other
	// federated modules associated with the applicationthat will create
	// the graph in conjunction with the `isolatedChunks`.
	const remoteChunks = [
	"appOne",
	"appTwo",
	"utilities"
	];

	// References to the endpoints that we need to get the configuration files
	// from to initialise the application again the current session.
	const configChunks = [
	"http://example.com/location.config.json", // Global location config.
	"../environment.config.json" // Per environment config.
	];

	// Grab our configuration files in parallel.
	const [location, { environment }] = await Promise.all(
	configChunks.map(chunk => fetch(chunk).then(response => response.json()))
	);

	// Reference our configuration files against the global window so that
	// our dynamic `publicPath` function can grab them when initialising our
	// bundles.
	window.__ENVIRONMENT__ = environment;
	window.__LOCATION__ = location;

	// Now that we have our configuration, lets get the javascript we need to
	// initialise the application. We parallelise the requests to keep things
	// speedy.
	await Promise.all([
	// Fetch the `remoteEntry.js` files for our federated dependancies.
	...remoteChunks
	.map(chunk => {
	const { href } = location[chunk][environment];
	return fetch(`${href}/remoteEntry.js`).then(response => response.text());
	}),
	// Get files dedicated to running this micro front-end in isolation
	// mode.
	...isolationChunks
	.map(chunk => fetch(`./${chunk}.js`)
	.then(response => response.text())
	)
	])
	.then(scripts => scripts.forEach(script => {
	// Now that we have our scripts, let's inject them onto the page
	// so that we can run out application initialisation sequence.
	const element = document.createElement("script");
	element.text = script;
	document.querySelector("body").appendChild(element);
	}));
	})();
	</script>
	</head>
	<body></body>
	</html>
	{
	"shell": {
	"development": {
	"href": "http://localhost:8000/"
	},
	"staging": {
	"href": "http://staging.shell.example.com/"
	},
	"production": {
	"href": "http://prod.shell.example.com/"
	}
	},
	"appOne": {
	"development": {
	"href": "http://localhost:8001/"
	},
	"staging": {
	"href": "http://staging.app-one.example.com/"
	},
	"production": {
	"href": "http://prod.app-one.example.com/"
	}
	},
	"appTwo": {
	"development": {
	"href": "http://localhost:8002/"
	},
	"staging": {
	"href": "http://staging.app-two.example.com/"
	},
	"production": {
	"href": "http://prod.app-two.example.com/"
	}
	},
	"utilities": {
	"development": {
	"href": "http://localhost:8003/"
	},
	"staging": {
	"href": "http://staging.utilities.example.com/"
	},
	"production": {
	"href": "http://prod.utilities.example.com/"
	}
	}
	}
	...

	/**
	* Allows static builds to change their `publicName` dynamically at run time rather
	* than build time. This allows builds to be environment agnostic, where we can
	* change from Staging, UAT, to Production with the same artefact and have the
	* `publicName` update accordingly via some run time configuration.
	* @class
	*/
	class DynamicPublicPathPlugin {
	/**
	* The Webpack hook to apply our plugin.
	* @parem {Object} compiler - The Webpack compiler.
	*/
	apply(compiler) {

	compiler.hooks.make.tap("MutateRuntime", (compilation) => {

	compilation.hooks.runtimeModule.tap("MutateRuntime", (module, chunk) => {

	const isPublicPathRuntimeModule = module.constructor.name === "PublicPathRuntimeModule";

	if (!isPublicPathRuntimeModule) { return; }

	console.log(`* Update "${chunk.name}" dynamic public path`);

	// We extract the variable "key" (the namespace to left of the equals sign)
	// and leave the rest behind as we are going to build our own new value
	// and assign it back to the variable.
	const [key] = module.getGeneratedCode().split("=");

	// Swap out the old static string value for a function that will run in
	// the browser session and create a public path based on the current
	// configuration.
	//
	// We create the `publicPath` from the "environment.config.json" and
	// "location.config.json" configuration files that are saved as global
	// variables in the browser `__ENVIRONEMENT__` and `__LOCATION__`.
	module._cachedGeneratedCode = `${key}=(function() {
	const { __LOCATION__, __ENVIRONEMENT__ } = window;
	const { href } = __LOCATION__.shell[__ENVIRONEMENT__];
	const publicPath = href + "/";

	return publicPath;
	})();`

	return module;

	});
	});
	}
	}

	...

	module.exports = async (_, args) => {
	...

	return {
	...

	plugins: [
	new ModuleFederationPlugin({
	...
	}),

	new DynamicPublicPathPlugin(),

	...

	]

	...
	};