Enable server-side rendering for ReactSpa template

templates/ReactSpa/ClientApp/boot-server.tsx

@@ -0,0 +1,34 @@
+import * as React from 'react';
+import { renderToString } from 'react-dom/server';
+import { match, RouterContext } from 'react-router';
+import createMemoryHistory from 'history/lib/createMemoryHistory';
+import { routes } from './routes';
+
+// The 'asp-prerender-module' tag helper invokes the following function when the React app is to
+// be prerendered on the server. It runs asynchronously, and issues a callback with the React app's
+// initial HTML and any other state variables.
+
+export default function (params: any): Promise<{ html: string }> {
+    return new Promise<{ html: string, globals: { [key: string]: any } }>((resolve, reject) => {
+        // Match the incoming request against the list of client-side routes, and reject if there was no match
+        match({ routes, location: params.location }, (error, redirectLocation, renderProps: any) => {
+            if (error) {
+                throw error;
+            }
+
+            // Build an instance of the application and perform an initial render.
+            // This will cause any async tasks (e.g., data access) to begin.
+            const history = createMemoryHistory(params.url);
+            const app = <RouterContext {...renderProps} />;
+            renderToString(app);
+
+            // Once the tasks are done, we can perform the final render
+            params.domainTasks.then(() => {
+                resolve({
+                    html: renderToString(app),
+                    globals: { /* Supply any other JSON-serializable data you want to make available on the client */ }
+                });
+            }, reject); // Also propagate any errors back into the host application
+        });
+    });
+}