Update watch demo to not start a new http server every compile (#101)

Author: Nikhil Thorat

scripts/watch-demo

@@ -26,12 +26,17 @@ const watchify = spawn(cmd, [startTsFilePath, '-p', '[tsify]', '-v', '--debug',
 watchify.stdout.pipe(process.stdout);
 watchify.stderr.pipe(process.stderr);
 
+let httpServerStarted = false;
+
 console.log('Waiting for initial compile...');
 watchify.stderr.on('data', (data) => {
   if (data.toString().includes(`written to ${path.dirname(startTsFilePath)}`)) {
-    const httpCmd = path.join('node_modules', '.bin', 'http-server');
-    const httpServer = spawn(httpCmd, ['-c-1'], { detached: false});
-    httpServer.stdout.pipe(process.stdout);
-    httpServer.stderr.pipe(process.stderr);
+    if (!httpServerStarted) {
+      const httpCmd = path.join('node_modules', '.bin', 'http-server');
+      const httpServer = spawn(httpCmd, ['-c-1'], { detached: false});
+      httpServer.stdout.pipe(process.stdout);
+      httpServer.stderr.pipe(process.stderr);
+      httpServerStarted = true;
+    }
   }
 });