add 'evict' event

index.js

@@ -1,9 +1,14 @@
+var events = require('events');
+var sys = require('sys');
+
 var LRU = exports.LRU = function (max) {
+    events.EventEmitter.call(this);
     this.cache = {}
     this.head = this.tail = null;
     this.length = 0;
     this.max = max || 1000;
 };
+sys.inherits(LRU, events.EventEmitter);
 
 LRU.prototype.remove = function (key) {
   var element = this.cache[key];
@@ -56,6 +61,8 @@ LRU.prototype.get = function (key) {
 
 LRU.prototype.evict = function () {
     if(!this.tail) { return; }
-    this.remove(this.tail);
+    var key = this.tail;
+    var element = this.remove(this.tail);
+    this.emit('evict', {key:key, value:element.value});
 };
 

test/lru-test.js

@@ -123,5 +123,23 @@ suite.addBatch({
   }
 });
 
+suite.addBatch({
+  "evict event": {
+    "'evict' event is fired when evicting old keys": function() {
+      var lru = new LRU.LRU(2);
+      var events = [];
+      lru.on('evict', function(element) { events.push(element); });
+
+      lru.set('foo1', 'bar1');
+      lru.set('foo2', 'bar2');
+      lru.set('foo3', 'bar3');
+      lru.set('foo4', 'bar4');
+
+      var expect = [{key:'foo1', value:'bar1'}, {key:'foo2', value:'bar2'}];
+      assert.deepEqual(events, expect);
+    }
+  }
+});
+
 suite.export(module);