feat: make the keyv object an emitter

src/KeyvLru.js

@@ -3,11 +3,12 @@
 import type { MapInterface } from '../flow/types/MapInterface';
 
 const lru = require('tiny-lru');
+const EventEmitter = require('events');
 
 /**
  * An adaptor from tiny-lru to a Map API.
  */
-class KeyvLru implements MapInterface {
+class KeyvLru extends EventEmitter implements MapInterface {
   // @TODO: Type this in a less generic way.
   cache: Object;
 
@@ -19,7 +20,16 @@ class KeyvLru implements MapInterface {
       expire?: number,
     } = { max: 500 }
   ) {
+    super();
     this.cache = lru(options.max, options.notify, options.ttl, options.expire);
+    if (options.notify) {
+      // This seems like a weird construct, but this is because tiny-lru passes
+      // the execution of this.cache.onchange to process.nextTick. nextTick
+      // expects a function.
+      this.cache.onchange = (event, serializedCache) => () => {
+        this.emit('change', event, serializedCache);
+      };
+    }
   }
 
   clear(): void {

src/KeyvLru.test.js

@@ -54,4 +54,16 @@ describe('KeyvLru', () => {
       expect(sut.cache).toHaveLength(0);
     });
   });
+  test('events', done => {
+    expect.assertions(2);
+    const sut = new KeyvLru({ max: 10, notify: true });
+    sut.on('change', (event, serializedCache) => {
+      expect(event).toBe('set');
+      expect(serializedCache).toBe(
+        '{"expire":0,"max":10,"notify":true,"ttl":0,"cache":{"foo":{"next":"","previous":"","value":{"bar":true}}},"expires":{},"first":"foo","last":"foo","length":1}'
+      );
+      done();
+    });
+    sut.set('foo', { bar: true });
+  });
 });