Support set on Maps

.travis.yml

@@ -1,8 +1,8 @@
 language: node_js
 node_js:
-  - '6'
   - '8'
   - '10'
+  - '12'
   - 'lts/*'
 # Send coverage data to Coveralls
 after_script: "cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js"

index.d.ts

@@ -30,6 +30,10 @@ declare type MapSpec<K, V> = {
     $add: Array<[K, V]>;
 } | {
     $remove: K[];
+} | {
+    [key: string]: {
+        $set: V;
+    };
 };
 declare type SetSpec<T> = {
     $add: T[];

index.ts

@@ -343,7 +343,8 @@ type ArraySpec<T, C extends CustomCommands<object>> =
 
 type MapSpec<K, V> =
   | { $add: Array<[K, V]> }
-  | { $remove: K[] };
+  | { $remove: K[] }
+  | { [key: string]: { $set: V } };
 
 type SetSpec<T> =
   | { $add: T[] }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "immutability-helper",
-  "version": "3.0.0",
+  "version": "3.0.1",
   "description": "mutate a copy of data without changing the original source",
   "main": "index.js",
   "typings": "index.d.ts",

test.ts

@@ -163,6 +163,13 @@ describe('immutability-helper module', () => {
       expect(result).toEqual({a: 1, b: undefined});
       expect(Object.keys(result).length).toEqual(2);
     });
+    it('works on Map (E2E)', () => {
+      const state = new Map([['foo', 'FOO'], ['bar', 'BAR']]);
+      const modified = update(state, {foo: {$set: 'OFO' }});
+      expect(state).toEqual(new Map([['foo', 'FOO'], ['bar', 'BAR']]));
+      expect(modified).toEqual(new Map([['foo', 'OFO'], ['bar', 'BAR']]));
+      expect(state).not.toBe(modified);
+    });
   });
 
   describe('$toggle', () => {