add peek(key) function

isaacs · Mar 25, 2013 · 5b43b23 · 5b43b23
1 parent e57ac87
commit 5b43b23
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Showing 3 changed files with 34 additions and 13 deletions.
diff --git a/README.md b/README.md
@@ -60,6 +60,15 @@ away.
     Both of these will update the "recently used"-ness of the key.
     They do what you think.
 
+* `peek(key)`
+
+    Returns the key value (or `undefined` if not found) without
+    updating the "recently used"-ness of the key.
+
+    (If you find yourself using this a lot, you *might* be using the
+    wrong sort of data structure, but there are some use cases where
+    it's handy.)
+
 * `del(key)`
 
     Deletes a key out of the cache.

diff --git a/lib/lru-cache.js b/lib/lru-cache.js
@@ -191,22 +191,34 @@ function LRUCache (options) {
     }
     return true
   }
-
-  this._get = function (key) {
-    return cache[key]
+
+  this.peek = function (key) {
+    var hit = get(key)
+    return hit && hit.value
   }
 
   this.get = function (key) {
-    if (!hOP(cache, key)) return
+    var hit = get(key)
+    var ret
+    if (hit) {
+      delete lruList[hit.lu]
+      hit.lu = mru ++
+      lruList[hit.lu] = hit
+      ret = hit.value
+    }
+    return ret
+  }
+
+  // Does not update least-recently-used status
+  function get(key) {
     var hit = cache[key]
-    if (maxAge && (Date.now() - hit.now > maxAge)) {
-      this.del(key)
-      return allowStale ? hit.value : undefined
+    if (hit) {
+      if (maxAge && (Date.now() - hit.now > maxAge)) {
+        del(hit)
+        if (!allowStale) hit = undefined
+      }
     }
-    delete lruList[hit.lu]
-    hit.lu = mru ++
-    lruList[hit.lu] = hit
-    return hit.value
+    return hit
   }
 
   this.del = function (key) {

diff --git a/test/basic.js b/test/basic.js
@@ -300,12 +300,12 @@ test("stale", function(t) {
   }, 15)
 })
 
-test("least recently set w/ _get", function (t) {
+test("least recently set w/ peek", function (t) {
   var cache = new LRU(2)
   cache.set("a", "A")
   cache.set("b", "B")
+  t.equal(cache.peek("a"), "A")
   cache.set("c", "C")
-  cache._get("a")
   t.equal(cache.get("c"), "C")
   t.equal(cache.get("b"), "B")
   t.equal(cache.get("a"), undefined)