WIP: fix error when checking EventRegistration callbacks

Author: jsayol

src/database/core/view/EventRegistration.ts

@@ -1,6 +1,6 @@
 import { DataSnapshot } from '../../api/DataSnapshot';
 import { DataEvent, CancelEvent, Event } from './Event';
-import { contains, getCount, getAnyKey } from '../../../utils/obj';
+import { contains, getCount, getAnyKey, every } from '../../../utils/obj';
 import { assert } from '../../../utils/assert';
 import { Path } from '../util/Path';
 import { Change } from './Change';
@@ -241,9 +241,7 @@ export class ChildEventRegistration implements EventRegistration {
             );
           } else {
             // Exact match on each key.
-            return this.callbacks_.every(<any>function (cb, eventType) {
-              return other.callbacks_[eventType] === cb;
-            });
+            return every(this.callbacks_, (eventType, cb) => other.callbacks_[eventType] === cb);
           }
         }
       }

src/utils/obj.ts

@@ -110,4 +110,23 @@ export const getValues = function(obj) {
     res[i++] = obj[key];
   }
   return res;
-};
+};
+
+/**
+ * Tests whether every key/value pair in an object pass the test implemented
+ * by the provided function
+ *
+ * @param {?Object.<K,V>} obj Object to test.
+ * @param {!function(K, V)} fn Function to call for each key and value.
+ * @template K,V
+ */
+export const every = function<V>(obj: Object, fn: (k: string, v?: V) => boolean): boolean {
+  for (let key in obj) {
+    if (Object.prototype.hasOwnProperty.call(obj, key)) {
+      if (!fn(key, obj[key])) {
+        return false;
+      }
+    }
+  }
+  return true;
+};