From 9cffe158a70f4945a6bf000dace4eddf4ca2c344 Mon Sep 17 00:00:00 2001
From: James Halliday <substack@gmail.com>
Date: Thu, 26 Aug 2010 19:53:16 -0800
Subject: [PATCH] memoization for keys, values, length

---
 lib/hash.js  | 37 ++++++++++++++++++++++---------------
 package.json |  2 +-
 test/hash.js |  8 ++++++++
 3 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/lib/hash.js b/lib/hash.js
index cf3c06d..a55c478 100644
--- a/lib/hash.js
+++ b/lib/hash.js
@@ -14,6 +14,7 @@ function Hash (hash, extra) {
             Object.keys(hash).forEach(function (key) {
                 f.call(hash, hash[key], key);
             });
+            memoized = {};
             return self;
         },
         filter : function (f) {
@@ -37,31 +38,34 @@ function Hash (hash, extra) {
             Object.keys(h).forEach(function (key) {
                 hash[key] = h[key];
             });
+            memoized = {};
             return self;
         },
         merge : function (h) {
-            var acc = {};
-            Object.keys(hash).forEach(function (key) {
-                acc[key] = hash[key];
-            });
-            Object.keys(h).forEach(function (key) {
-                acc[key] = h[key];
-            });
-            hash = acc;
-            return self;
+            return self.clone.update(h);
+        },
+        tap : function (f) {
+            f.call(self, hash);
+            memoized = {};
         },
-        tap : function (f) { f.call(self, hash) },
         end : hash,
         items : hash
     };
     
+    var memoized = {};
     Object.defineProperty(self, 'keys', { get : function () {
-        return Object.keys(hash);
+        if (memoized.keys === undefined) {
+            memoized.keys = Object.keys(hash);
+        }
+        return memoized.keys
     } });
     
     Object.defineProperty(self, 'values', { get : function () {
-        return Object.keys(hash)
-            .map(function (key) { return hash[key] })
+        if (memoized.values === undefined) {
+            memoized.values = Object.keys(hash)
+                .map(function (key) { return hash[key] });
+        }
+        return memoized.values;
     } });
     
     Object.defineProperty(self, 'clone', { get : function () {
@@ -73,7 +77,10 @@ function Hash (hash, extra) {
     } });
     
     Object.defineProperty(self, 'length', { get : function () {
-        return Object.keys(hash).length;
+        if (memoized.length === undefined) {
+            memoized.length = Object.keys(hash).length;
+        }
+        return memoized.length;
     } });
     
     return self;
@@ -108,6 +115,6 @@ Hash.reduce = function (ref, f, acc) {
 Hash.concat = function (xs) {
     var hash = Hash({});
     xs.forEach(function (x) { hash.update(x) });
-    return hash;
+    return hash.items;
 };
 
diff --git a/package.json b/package.json
index faa42c3..393d5fc 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
     "name" : "traverse",
-    "version" : "0.0.7",
+    "version" : "0.0.8",
     "description" : "Traverse and transform objects by visiting every node on a recursive walk.",
     "author" : "James Halliday",
     "modules" : {
diff --git a/test/hash.js b/test/hash.js
index f59d739..02b57cf 100755
--- a/test/hash.js
+++ b/test/hash.js
@@ -57,5 +57,13 @@ exports['hash traversal'] = function (assert) {
     assert.equal(ref1.a, 1);
     assert.equal(ref1.b, 2);
     
+    var merged = hash3.merge({ c : 3.14, d : 4 });
+    assert.equal(merged.items.a, 0);
+    assert.equal(merged.items.b, 2);
+    assert.equal(merged.items.c, 3.14);
+    assert.equal(merged.items.d, 4);
+    assert.equal(merged.length, 4);
+    assert.equal(hash3.items.c, 3);
+    assert.equal(hash3.length, 3);
 };