From 090fb09955b63cfb186c7a78ce80dc49fff5396c Mon Sep 17 00:00:00 2001
From: John-David Dalton <john.david.dalton@gmail.com>
Date: Thu, 6 Dec 2012 23:09:41 -0800
Subject: [PATCH] Optimize `_.union`.

Former-commit-id: 0cba8cac81a621b1fdbe8868ab406a30eb1d743f
---
 lodash.js    |  6 ++++--
 perf/perf.js | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/lodash.js b/lodash.js
index 1664a1296..66a2f605c 100644
--- a/lodash.js
+++ b/lodash.js
@@ -3140,11 +3140,13 @@
       if (isLarge) {
         // manually coerce `computed` to a string because `hasOwnProperty`, in
         // some older versions of Firefox, coerces objects incorrectly
-        seen = hasOwnProperty.call(cache, computed + '') ? cache[computed] : (cache[computed] = []);
+        var inited = hasOwnProperty.call(cache, computed + '')
+          ? !(seen = cache[computed])
+          : (seen = []);
       }
       if (isSorted
             ? !index || seen[seen.length - 1] !== computed
-            : indexOf(seen, computed) < 0
+            : inited || indexOf(seen, computed) < 0
           ) {
         if (callback || isLarge) {
           seen.push(computed);
diff --git a/perf/perf.js b/perf/perf.js
index a8d80a108..a53ea27a9 100644
--- a/perf/perf.js
+++ b/perf/perf.js
@@ -1631,6 +1631,42 @@
       )
   );
 
+  suites.push(
+    Benchmark.Suite('`_.union` iterating an array of 50 elements')
+      .add(buildName, {
+        'fn': 'lodash.union(twentyFiveValues, twentyFiveValues2);',
+        'teardown': 'function multiArrays(){}'
+      })
+      .add(otherName, {
+        'fn': '_.union(twentyFiveValues, twentyFiveValues2);',
+        'teardown': 'function multiArrays(){}'
+      })
+  );
+
+  suites.push(
+    Benchmark.Suite('`_.union` iterating an array of 75 elements')
+      .add(buildName, {
+        'fn': 'lodash.union(fiftyValues, twentyFiveValues2);',
+        'teardown': 'function multiArrays(){}'
+      })
+      .add(otherName, {
+        'fn': '_.union(fiftyValues, twentyFiveValues2);',
+        'teardown': 'function multiArrays(){}'
+      })
+  );
+
+  suites.push(
+    Benchmark.Suite('`_.union` iterating an array of 100 elements')
+      .add(buildName, {
+        'fn': 'lodash.union(seventyFiveValues, twentyFiveValues2);',
+        'teardown': 'function multiArrays(){}'
+      })
+      .add(otherName, {
+        'fn': '_.union(seventyFiveValues, twentyFiveValues2);',
+        'teardown': 'function multiArrays(){}'
+      })
+  );
+
   /*--------------------------------------------------------------------------*/
 
   suites.push(