Update README and fixes

README.md

@@ -7,7 +7,14 @@
 - 📊 Have some drivers for `firebase realtime db` or any storage libraries...
 
 ### Basic example
+#### Node or browser
 ```ts
+// ES6
+import { Queryable } from 'linq-fns';
+
+// ES5
+const Queryable = require('linq-fns').Queryable;
+
 let query = Queryable
  .from(nations)
  .join(continents, (x, y) => x.areaId === y.id)
@@ -28,6 +35,25 @@ asyncData.then(data => {
 });
 ```
 
+#### Firebase
+``` ts
+const FireBaseQueryale = require('linq-fns').FireBaseQueryale;
+const admin = require('firebase-admin');
+const serviceAccount = require('./serviceAccountKey');
+
+admin.initializeApp({
+ credential: admin.credential.cert(serviceAccount),
+ databaseURL: 'https://xxx.firebaseio.com'
+});
+
+const db = admin.database();
+const firebaseQuery = new FireBaseQueryale(db);
+
+const postsQuery = firebaseQuery.getRepository('<rootTable>.<childTables>.<child...>');
+// Then using like Queryable Apis 
+
+```
+
 ### Process
 - [x] from
 - [x] where

src/drivers/linq-fns-firebase.ts

@@ -33,6 +33,7 @@ export class FireBaseQueryale {
  }
 
  private convert<T>(objData: Object): T[] {
+ if (!objData) return [];
  return Object.keys(objData).map(prop => {
  objData[prop]['__id'] = prop;
  return objData[prop];