Add eviction handler

README.md

@@ -132,6 +132,11 @@ Immediately remove a key from the cache.
 ###`#expire(key, [ms=0])`
 Update the expire time for a key. You can also use any valid [ms](https://github.com/rauchg/ms.js) string for a timeout.
 
+###`#on('expiration', function)`
+Add a callback for handling expiration events. The handler will be passed a single parameter,
+the key name that was just expired. Note, the handler is called AFTER the key has been removed
+from the Receptacle.
+
 ###`#clear()`
 Remove all keys from the cache.
 

index.d.ts

@@ -29,6 +29,12 @@ namespace Receptacle {
         key: string;
         value: T;
     }
+
+    export Handler(key: string) : void
+
+    export enum Events {
+        eviction,
+    } 
 }
 
 class Receptacle<T, X = undefined> {
@@ -37,6 +43,7 @@ class Receptacle<T, X = undefined> {
     public max: number;
     public items: Receptacle.Items<T>[];
     public size: number;
+    public on(event: Receptacle.Event, handler: Receptacle.Handler): void;
     public has(key: string): boolean;
     public get(key: string): T|null;
     public meta(key: string): X|undefined;

index.js

@@ -3,7 +3,9 @@
 module.exports = Receptacle
 var toMS = require('ms')
 var cache = Receptacle.prototype
+console.dir(cache)
 var counter = new Date() % 1e9
+var EventEmitter = require('events')
 
 function getUID () { return (Math.random() * 1e9 >>> 0) + (counter++) }
 
@@ -21,6 +23,7 @@ function Receptacle (options) {
   this.max = options.max || Infinity
   this.items = options.items || []
   this._lookup = {}
+  this._events = new EventEmitter()
   this.size = this.items.length
   this.lastModified = new Date(options.lastModified || new Date())
 
@@ -34,6 +37,17 @@ function Receptacle (options) {
   }
 }
 
+/**
+ * Currently only the evict type is supported.
+ *
+ * @param {String} event - the event name.
+ * @param {Receptacle.Event} handler - the event handler
+ * @return {Boolean}
+ */
+cache.on = function (event, handler) {
+  return this._events.on(event, handler.bind(this))
+}
+
 /**
  * Tests if a key is currently in the cache.
  * Does not check if slot is empty.
@@ -144,7 +158,10 @@ cache.expire = function (key, ttl) {
   if (typeof ms === 'string') ms = toMS(ttl)
   if (typeof ms !== 'number') throw new TypeError('Expiration time must be a string or number.')
   clearTimeout(record.timeout)
-  record.timeout = setTimeout(this.delete.bind(this, record.key), ms)
+  record.timeout = setTimeout(function () {
+    this.delete(record.key)
+    this._events.emit('eviction', record.key)
+  }.bind(this), ms)
   record.expires = Number(new Date()) + ms
   return this
 }

test/main.test.js

@@ -34,6 +34,17 @@ describe('Receptacle', function () {
     })
   })
 
+  describe('#on', function () {
+    it('should emit an expiration event', function (done) {
+      var cache = new Receptacle()
+      cache.on('eviction', function (key) {
+        console.log('evicted: ' + key)
+        done()
+      })
+      cache.set('a', 1, { ttl: 200 })
+    })
+  })
+
   describe('#meta', function () {
     it('should return a set key', function () {
       var cache = new Receptacle()