diff --git a/src/observable/map/ApplyMap.ts b/src/observable/map/ApplyMap.ts
index f8d09914..1786873a 100644
--- a/src/observable/map/ApplyMap.ts
+++ b/src/observable/map/ApplyMap.ts
@@ -16,22 +16,17 @@ limitations under the License.
 
 import {BaseObservableMap} from "./BaseObservableMap";
 import {SubscriptionHandle} from "../BaseObservable";
-import {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
-import {JoinedMap} from "./JoinedMap";
-import {MappedMap} from "./MappedMap";
-import {FilteredMap} from "./FilteredMap";
-import {SortedMapList} from "../list/SortedMapList.js";
+import {BaseObservableMapDefaults} from "./BaseObservableMapDefaults";
 
 
 export class ApplyMap<K, V> extends BaseObservableMap<K, V> {
-    private _defaults = new BaseObservableMapDefaults<K, V>();
     private _source: BaseObservableMap<K, V>;
     private _subscription?: SubscriptionHandle;
     private _apply?: Apply<K, V>;
 
 
     constructor(source: BaseObservableMap<K, V>, apply?: Apply<K, V>) {
-        super();
+        super(new BaseObservableMapDefaults<K, V>());
         this._source = source;
         this._apply = apply;
     }
@@ -103,23 +98,6 @@ export class ApplyMap<K, V> extends BaseObservableMap<K, V> {
     get(key: K): V | undefined {
         return this._source.get(key);
     }
-
-    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
-        return this._defaults.join(this, ...otherMaps);
-    }
-
-    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V> {
-        return this._defaults.mapValues(this, mapper, updater);
-    }
-
-    sortValues(comparator: Comparator<V>): SortedMapList {
-        return this._defaults.sortValues(this, comparator);
-    }
-
-    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
-        return this._defaults.filterValues(this, filter);
-    }
-
 }
 
 type Apply<K, V> = (key: K, value: V, params?: any) => void;
\ No newline at end of file
diff --git a/src/observable/map/BaseObservableMap.ts b/src/observable/map/BaseObservableMap.ts
index 02dedce5..86300439 100644
--- a/src/observable/map/BaseObservableMap.ts
+++ b/src/observable/map/BaseObservableMap.ts
@@ -19,7 +19,8 @@ import {JoinedMap} from "../map/JoinedMap";
 import {MappedMap} from "../map/MappedMap";
 import {FilteredMap} from "../map/FilteredMap";
 import {SortedMapList} from "../list/SortedMapList.js";
-import {Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
+import type {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
+
 
 export interface IMapObserver<K, V> {
     onReset(): void;
@@ -29,6 +30,13 @@ export interface IMapObserver<K, V> {
 }
 
 export abstract class BaseObservableMap<K, V> extends BaseObservable<IMapObserver<K, V>> {
+    private _defaults: BaseObservableMapDefaults<K, V>;
+
+    constructor(defaults: BaseObservableMapDefaults<K, V>) {
+        super();
+        this._defaults = defaults;
+    }
+
     emitReset(): void {
         for(let h of this._handlers) {
             h.onReset();
@@ -54,17 +62,22 @@ export abstract class BaseObservableMap<K, V> extends BaseObservable<IMapObserve
         }
     }
 
-    // The following group of functions have a default implementation
-    // in the neighboring `BaseObservableMapDefaults.ts`. See the comment
-    // in that file for the explanation for why the default implementation
-    // isn't defined here. See the neighboring `ObservableMap.ts` for an
-    // example of how to easily add the boilerplate for using the default
-    // implementations of these functions in a class that extends
-    // this one (which is most likely what you want to do).
-    abstract join(...otherMaps: Array<typeof this>): JoinedMap<K, V>;
-    abstract mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V>;
-    abstract sortValues(comparator: Comparator<V>): SortedMapList;
-    abstract filterValues(filter: Filter<K, V>): FilteredMap<K, V>;
+    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
+        return this._defaults.join(this, ...otherMaps);
+    }
+
+    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V> {
+        return this._defaults.mapValues(this, mapper, updater);
+    }
+
+    sortValues(comparator: Comparator<V>): SortedMapList {
+        return this._defaults.sortValues(this, comparator);
+    }
+
+    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
+        return this._defaults.filterValues(this, filter);
+    }
+
 
     abstract [Symbol.iterator](): Iterator<[K, V]>;
     abstract get size(): number;
diff --git a/src/observable/map/BaseObservableMapDefaults.ts b/src/observable/map/BaseObservableMapDefaults.ts
index 46d9148e..444b8640 100644
--- a/src/observable/map/BaseObservableMapDefaults.ts
+++ b/src/observable/map/BaseObservableMapDefaults.ts
@@ -13,15 +13,14 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-import {BaseObservableMap} from "./BaseObservableMap";
+import type {BaseObservableMap} from "./BaseObservableMap";
 import {FilteredMap} from "./FilteredMap";
 import {MappedMap} from "./MappedMap";
 import {JoinedMap} from "./JoinedMap";
 import {SortedMapList} from "../list/SortedMapList.js";
 
 
-// This class is used as a default implementation of
-// the respective abstract functions in BaseObservableMap.
+// This class provides implementations of functions that are part of BaseObservableMap.
 // It is kept as its own class in its own file in order to avoid a circular
 // dependency between the classes that extend BaseObservableMap which are
 // instantiated here (i.e. `new JoinedMap()`).
diff --git a/src/observable/map/FilteredMap.ts b/src/observable/map/FilteredMap.ts
index b0ed2e82..267d0d35 100644
--- a/src/observable/map/FilteredMap.ts
+++ b/src/observable/map/FilteredMap.ts
@@ -16,20 +16,17 @@ limitations under the License.
 
 import {BaseObservableMap} from "./BaseObservableMap";
 import {SubscriptionHandle} from "../BaseObservable";
-import {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
-import {JoinedMap} from "./JoinedMap";
-import {MappedMap} from "./MappedMap";
-import {SortedMapList} from "../list/SortedMapList.js";
+import {BaseObservableMapDefaults, Filter} from "./BaseObservableMapDefaults";
+
 
 export class FilteredMap<K, V> extends BaseObservableMap<K, V> {
-    private _defaults = new BaseObservableMapDefaults<K, V>();
     private _source: BaseObservableMap<K, V>;
     private _filter: Filter<K, V>;
     private _included?: Map<K, boolean>;
     private _subscription?: SubscriptionHandle;
 
     constructor(source: BaseObservableMap<K, V>, filter: Filter<K, V>) {
-        super();
+        super(new BaseObservableMapDefaults<K, V>());
         this._source = source;
         this._filter = filter;
     }
@@ -162,22 +159,6 @@ export class FilteredMap<K, V> extends BaseObservableMap<K, V> {
             return value;
         }
     }
-
-    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
-        return this._defaults.join(this, ...otherMaps);
-    }
-
-    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V>{
-        return this._defaults.mapValues(this, mapper, updater);
-    }
-
-    sortValues(comparator: Comparator<V>): SortedMapList {
-        return this._defaults.sortValues(this, comparator);
-    }
-
-    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
-        return this._defaults.filterValues(this, filter);
-    }
 }
 
 class FilterIterator<K, V> {
diff --git a/src/observable/map/JoinedMap.ts b/src/observable/map/JoinedMap.ts
index d4164f79..b343d22f 100644
--- a/src/observable/map/JoinedMap.ts
+++ b/src/observable/map/JoinedMap.ts
@@ -15,20 +15,16 @@ limitations under the License.
 */
 
 import {BaseObservableMap} from "./BaseObservableMap";
-import {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
-import {FilteredMap} from "./FilteredMap";
-import {MappedMap} from "./MappedMap";
-import {SortedMapList} from "../list/SortedMapList.js";
+import {BaseObservableMapDefaults} from "./BaseObservableMapDefaults";
 import {SubscriptionHandle} from "../BaseObservable";
 
 
 export class JoinedMap<K, V> extends BaseObservableMap<K, V> {
-    private _defaults = new BaseObservableMapDefaults<K, V>();
     protected _sources: BaseObservableMap<K, V>[];
     private _subscriptions?: SourceSubscriptionHandler<K, V>[];
 
     constructor(sources: BaseObservableMap<K, V>[]) {
-        super();
+        super(new BaseObservableMapDefaults<K, V>());
         this._sources = sources;
     }
 
@@ -133,23 +129,6 @@ export class JoinedMap<K, V> extends BaseObservableMap<K, V> {
         }
         return undefined;
     }
-
-    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
-        return this._defaults.join(this, ...otherMaps);
-    }
-
-    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V> {
-        return this._defaults.mapValues(this, mapper, updater);
-    }
-
-    sortValues(comparator: Comparator<V>): SortedMapList {
-        return this._defaults.sortValues(this, comparator);
-    }
-
-    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
-        return this._defaults.filterValues(this, filter);
-    }
-
 }
 
 class JoinedIterator<K, V> implements Iterator<[K, V]> {
diff --git a/src/observable/map/LogMap.ts b/src/observable/map/LogMap.ts
index 7b857678..6db70f01 100644
--- a/src/observable/map/LogMap.ts
+++ b/src/observable/map/LogMap.ts
@@ -15,23 +15,19 @@ limitations under the License.
 */
 
 import {BaseObservableMap} from "./BaseObservableMap";
-import {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
-import {FilteredMap} from "./FilteredMap";
-import {MappedMap} from "./MappedMap";
-import {JoinedMap} from "./JoinedMap";
-import {SortedMapList} from "../list/SortedMapList.js";
+import {BaseObservableMapDefaults} from "./BaseObservableMapDefaults";
 import {SubscriptionHandle} from "../BaseObservable";
 import {ILogItem, LabelOrValues} from "../../logging/types";
 import {LogLevel} from "../../logging/LogFilter";
 
+
 export class LogMap<K, V> extends BaseObservableMap<K, V> {
-    private _defaults = new BaseObservableMapDefaults<K, V>();
     private _source: BaseObservableMap<K, V>;
     private _subscription?: SubscriptionHandle;
     private _log: ILogItem;
 
     constructor(source: BaseObservableMap<K, V>, log: ILogItem) {
-        super();
+        super(new BaseObservableMapDefaults<K, V>());
         this._source = source;
         this._log = log;
     }
@@ -84,21 +80,4 @@ export class LogMap<K, V> extends BaseObservableMap<K, V> {
     get(key: K): V | undefined{
         return this._source.get(key);
     }
-
-    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
-        return this._defaults.join(this, ...otherMaps);
-    }
-
-    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V> {
-        return this._defaults.mapValues(this, mapper, updater);
-    }
-
-    sortValues(comparator: Comparator<V>): SortedMapList {
-        return this._defaults.sortValues(this, comparator);
-    }
-
-    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
-        return this._defaults.filterValues(this, filter);
-    }
-
 }
diff --git a/src/observable/map/MappedMap.ts b/src/observable/map/MappedMap.ts
index 3d9e3a3c..72115d84 100644
--- a/src/observable/map/MappedMap.ts
+++ b/src/observable/map/MappedMap.ts
@@ -15,18 +15,15 @@ limitations under the License.
 */
 
 import {BaseObservableMap} from "./BaseObservableMap";
-import {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
-import {JoinedMap} from "./JoinedMap";
-import {FilteredMap} from "./FilteredMap";
-import {SortedMapList} from "../list/SortedMapList.js";
+import {BaseObservableMapDefaults, Mapper, Updater} from "./BaseObservableMapDefaults";
 import {SubscriptionHandle} from "../BaseObservable";
 
+
 /*
 so a mapped value can emit updates on it's own with this._emitSpontaneousUpdate that is passed in the mapping function
 how should the mapped value be notified of an update though? and can it then decide to not propagate the update?
 */
 export class MappedMap<K, V> extends BaseObservableMap<K, V> {
-    private _defaults = new BaseObservableMapDefaults<K, V>();
     private _source: BaseObservableMap<K, V>;
     private _mapper: Mapper<V>;
     private _updater?: Updater<V>;
@@ -39,7 +36,7 @@ export class MappedMap<K, V> extends BaseObservableMap<K, V> {
         mapper: Mapper<V>,
         updater?: Updater<V>
     ) {
-        super();
+        super(new BaseObservableMapDefaults<K, V>());
         this._source = source;
         this._mapper = mapper;
         this._updater = updater;
@@ -113,20 +110,4 @@ export class MappedMap<K, V> extends BaseObservableMap<K, V> {
     get(key: K): V | undefined {
         return this._mappedValues.get(key);
     }
-
-    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
-        return this._defaults.join(this, ...otherMaps);
-    }
-
-    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V>{
-        return this._defaults.mapValues(this, mapper, updater);
-    }
-
-    sortValues(comparator: Comparator<V>): SortedMapList {
-        return this._defaults.sortValues(this, comparator);
-    }
-
-    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
-        return this._defaults.filterValues(this, filter);
-    }
 }
\ No newline at end of file
diff --git a/src/observable/map/ObservableMap.ts b/src/observable/map/ObservableMap.ts
index 4b98c089..9527ffdd 100644
--- a/src/observable/map/ObservableMap.ts
+++ b/src/observable/map/ObservableMap.ts
@@ -15,19 +15,14 @@ limitations under the License.
 */
 
 import {BaseObservableMap} from "./BaseObservableMap";
-import {BaseObservableMapDefaults, Mapper, Updater, Comparator, Filter} from "./BaseObservableMapDefaults";
-import {JoinedMap} from "./JoinedMap";
-import {MappedMap} from "./MappedMap";
-import {FilteredMap} from "./FilteredMap";
-import {SortedMapList} from "../list/SortedMapList.js";
+import {BaseObservableMapDefaults} from "./BaseObservableMapDefaults";
 
 
 export class ObservableMap<K, V> extends BaseObservableMap<K, V> {
-    private _defaults = new BaseObservableMapDefaults<K, V>();
     private readonly _values: Map<K, V>;
 
     constructor(initialValues?: (readonly [K, V])[]) {
-        super();
+        super(new BaseObservableMapDefaults<K, V>());
         this._values = new Map(initialValues);
     }
 
@@ -98,22 +93,6 @@ export class ObservableMap<K, V> extends BaseObservableMap<K, V> {
     keys(): Iterator<K> {
         return this._values.keys();
     }
-
-    join(...otherMaps: Array<typeof this>): JoinedMap<K, V> {
-        return this._defaults.join(this, ...otherMaps);
-    }
-
-    mapValues(mapper: Mapper<V>, updater?: Updater<V>): MappedMap<K, V> {
-        return this._defaults.mapValues(this, mapper, updater);
-    }
-
-    sortValues(comparator: Comparator<V>): SortedMapList {
-        return this._defaults.sortValues(this, comparator);
-    }
-
-    filterValues(filter: Filter<K, V>): FilteredMap<K, V> {
-        return this._defaults.filterValues(this, filter);
-    }
 };
 
 // eslint-disable-next-line @typescript-eslint/explicit-function-return-type