Add events to memoize

PR-URL: #284

lib/memoize.js

@@ -18,7 +18,8 @@ const memoize = (
       return;
     }
     fn(...args, (err, data) => {
-      cache.set(key, { err, data });
+      memoized.add(key, err, data);
+      memoized.emit('memoize', key, err, data);
       callback(err, data);
     });
   };
@@ -30,22 +31,33 @@ const memoize = (
     size: 0,
     maxSize: 0,
     maxCount: 0,
+    events: {
+      timeout: null,
+      memoize: null,
+      overflow: null,
+      add: null,
+      del: null,
+      clear: null
+    }
   };
 
   Object.setPrototypeOf(memoized, Memoized.prototype);
   return Object.assign(memoized, fields);
 };
 
 Memoized.prototype.clear = function() {
+  this.emit('clear');
   this.cache.clear();
 };
 
 Memoized.prototype.add = function(key, err, data) {
+  this.emit('add', err, data);
   this.cache.set(key, { err, data });
   return this;
 };
 
 Memoized.prototype.del = function(key) {
+  this.emit('del', key);
   this.cache.delete(key);
   return this;
 };
@@ -56,6 +68,28 @@ Memoized.prototype.get = function(key, callback) {
   return this;
 };
 
+Memoized.prototype.on = function(
+  eventName, // string
+  listener // function, handler
+  // on('memoize', function(err, data))
+  // on('add', function(key, err, data))
+  // on('del', function(key))
+  // on('clear', function())
+) {
+  if (eventName in this.events) {
+    this.events[eventName] = listener;
+  }
+};
+
+Memoized.prototype.emit = function(
+  // Emit Collector events
+  eventName, // string
+  ...args // rest arguments
+) {
+  const event = this.events[eventName];
+  if (event) event(...args);
+};
+
 module.exports = {
   memoize,
 };

test/memoize.js

@@ -19,6 +19,11 @@ tap.test('memoize', (test) => {
 
   const memoizedGetData = metasync.memoize(getData);
 
+  const keys = [];
+  memoizedGetData.on('memoize', (key) => {
+    keys.push(key);
+  });
+
   memoizedGetData('file1', (err, data) => {
     test.error(err);
     test.strictSame(data, storage.file1);
@@ -31,6 +36,7 @@ tap.test('memoize', (test) => {
         memoizedGetData('file2', (err, data) => {
           test.error(err);
           test.strictSame(data, storage.file2);
+          test.strictSame(keys, ['file1', 'file2']);
           test.end();
         });
       });
@@ -53,6 +59,11 @@ tap.test('memoize clear cache', (test) => {
 
   const memoizedGetData = metasync.memoize(getData);
 
+  let onClear = false;
+  memoizedGetData.on('clear', () => {
+    onClear = true;
+  });
+
   memoizedGetData('file1', (err, data) => {
     test.error(err);
     test.strictSame(data, storage.file1);
@@ -61,6 +72,7 @@ tap.test('memoize clear cache', (test) => {
     memoizedGetData('file1', (err, data) => {
       test.error(err);
       test.strictSame(data, Buffer.from('changed'));
+      test.strictSame(onClear, true);
       test.end();
     });
   });
@@ -81,6 +93,11 @@ tap.test('memoize cache del', (test) => {
 
   const memoizedGetData = metasync.memoize(getData);
 
+  let onDel = false;
+  memoizedGetData.on('del', () => {
+    onDel = true;
+  });
+
   memoizedGetData('file1', (err, data) => {
     test.error(err);
     test.strictSame(data, storage.file1);
@@ -89,6 +106,7 @@ tap.test('memoize cache del', (test) => {
     memoizedGetData('file1', (err, data) => {
       test.error(err);
       test.strictSame(data, Buffer.from('changed'));
+      test.strictSame(onDel, true);
       test.end();
     });
   });
@@ -104,11 +122,17 @@ tap.test('memoize cache add', (test) => {
 
   const memoizedGetData = metasync.memoize(getData);
 
+  let onAdd = false;
+  memoizedGetData.on('add', () => {
+    onAdd = true;
+  });
+
   const file1 = Buffer.from('added');
   memoizedGetData.add('file1', null, file1);
   memoizedGetData('file1', (err, data) => {
     test.error(err);
     test.strictSame(data, Buffer.from('added'));
+    test.strictSame(onAdd, true);
     test.end();
   });
 });