Add default values for translationsUrl

packages/translation/src/manager.ts

@@ -8,7 +8,7 @@ import { ITranslator, TranslationBundle, TranslatorConnector } from './tokens';
  * Translation Manager
  */
 export class TranslationManager implements ITranslator {
-  constructor(translationsUrl?: string, stringsPrefix?: string) {
+  constructor(translationsUrl: string = '', stringsPrefix?: string) {
     this._connector = new TranslatorConnector(translationsUrl);
     this._stringsPrefix = stringsPrefix || '';
     this._englishBundle = new Gettext({ stringsPrefix: this._stringsPrefix });

packages/translation/src/server.ts

@@ -13,8 +13,8 @@ import { ServerConnection } from '@jupyterlab/services';
  * @returns The response body interpreted as JSON
  */
 export async function requestTranslationsAPI<T>(
+  translationsUrl: string = '',
   locale = '',
-  translationsUrl?: string,
   init: RequestInit = {}
 ): Promise<T> {
   // Make request to Jupyter API

packages/translation/src/tokens.ts

@@ -24,7 +24,7 @@ export const ITranslatorConnector = new Token<ITranslatorConnector>(
 export class TranslatorConnector
   extends DataConnector<Language, Language, { language: string }>
   implements ITranslatorConnector {
-  constructor(translationsUrl?: string) {
+  constructor(translationsUrl: string = '') {
     super();
     this._translationsUrl = translationsUrl;
   }