move frontend app into separate file

frontend/src/app.js

@@ -0,0 +1,25 @@
+import { HttpClient } from './services/http-client/http-client';
+import { HtmlHelpers } from './services/html-helpers/html-helpers';
+import { I18n } from './services/i18n/i18n';
+import { UtilRegistry } from './services/util-registry/util-registry';
+
+export class App {
+  httpClient = new HttpClient();
+  htmlHelpers = new HtmlHelpers();
+  i18n = new I18n();
+  utilRegistry = new UtilRegistry();
+
+  constructor() {
+    this.utilRegistry.setApp(this);
+  }
+
+  registerUtilities(utils) {
+    if (!Array.isArray(utils)) {
+      throw new Error('Utils are expected to be passed as array!');
+    }
+
+    utils.forEach((util) => {
+      this.utilRegistry.register(util);
+    });
+  }
+}

frontend/src/main.js

@@ -1,27 +1,8 @@
-import { HttpClient } from './services/http-client/http-client';
+import { App } from './app';
-import { HtmlHelpers } from './services/html-helpers/html-helpers';
-import { I18n } from './services/i18n/i18n';
-import { UtilRegistry } from './services/util-registry/util-registry';
-
-// import utils
 import Utils from './utils/utils';
 
-class App {
-  httpClient = new HttpClient();
-  htmlHelpers = new HtmlHelpers();
-  i18n = new I18n();
-  utilRegistry = new UtilRegistry();
-
-  constructor() {
-    this.utilRegistry.setApp(this);
-
-    Utils.forEach(util => {
-      this.utilRegistry.register(util);
-    });
-  }
-}
-
 export const app = new App();
+app.registerUtilities(Utils);
 
 // attach the app to window to be able to get a hold of the
 // app instance from the shakespearean templates