From b0f291973b579a63252779f72e004e663fbba8ab Mon Sep 17 00:00:00 2001
From: Tim Schaub <tim.schaub@gmail.com>
Date: Sat, 7 Oct 2017 10:04:19 -0600
Subject: [PATCH] Method for peeking at the newest cache entry key

---
 src/ol/structs/lrucache.js            |  9 +++++++++
 test/spec/ol/structs/lrucache.test.js | 24 ++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/src/ol/structs/lrucache.js b/src/ol/structs/lrucache.js
index e0f74ec850..046e8f5adf 100644
--- a/src/ol/structs/lrucache.js
+++ b/src/ol/structs/lrucache.js
@@ -196,6 +196,15 @@ ol.structs.LRUCache.prototype.peekLastKey = function() {
 };
 
 
+/**
+ * Get the key of the newest item in the cache.  Throws if the cache is empty.
+ * @return {string} The newest key.
+ */
+ol.structs.LRUCache.prototype.peekFirstKey = function() {
+  return this.newest_.key_;
+};
+
+
 /**
  * @return {T} value Value.
  */
diff --git a/test/spec/ol/structs/lrucache.test.js b/test/spec/ol/structs/lrucache.test.js
index fd25890692..3b4453bee3 100644
--- a/test/spec/ol/structs/lrucache.test.js
+++ b/test/spec/ol/structs/lrucache.test.js
@@ -164,6 +164,30 @@ describe('ol.structs.LRUCache', function() {
     });
   });
 
+  describe('#peekFirstKey()', function() {
+    it('returns the newest key in the cache', function() {
+      var cache = new ol.structs.LRUCache();
+      cache.set('oldest', 'oldest');
+      cache.set('oldish', 'oldish');
+      cache.set('newish', 'newish');
+      cache.set('newest', 'newest');
+      expect(cache.peekFirstKey()).to.eql('newest');
+    });
+
+    it('works if the cache has one item', function() {
+      var cache = new ol.structs.LRUCache();
+      cache.set('key', 'value');
+      expect(cache.peekFirstKey()).to.eql('key');
+    });
+
+    it('throws if the cache is empty', function() {
+      var cache = new ol.structs.LRUCache();
+      expect(function() {
+        cache.peekFirstKey();
+      }).to.throwException();
+    });
+  });
+
   describe('peeking at the last value', function() {
     it('returns the last key', function() {
       fillLRUCache(lruCache);