Add Hash.prototype.index which returns the first found property that has a specific value. Closes #8528. [Thomas Fuchs, slusarz, Mislav Marohnic]

CHANGELOG

@@ -1,5 +1,11 @@
 *SVN*
 
+* Add Hash.prototype.index which returns the first found property that has a specific value.  Closes #8528.  [Thomas Fuchs, slusarz, Mislav Marohnić]
+  Examples:
+    var hash = $H({a:1,b:'2'});
+    hash.index(1)   // -> 'a'
+    hash.index('1') // -> undefined
+
 * Ensure HTMLElement exists before creating Element.extend.  [Tobie Langel]
 
 * Add Number.prototype.round/ceil/floor/abs as an aliases to the respective methods in Math. Refactor to seperate number extensions from base.js.  [Thomas Fuchs]

src/hash.js

@@ -62,6 +62,13 @@ Object.extend(Hash.prototype, {
     return this.pluck('value');
   },
   
+  index: function(value) {
+    var match = this.detect(function(pair) { 
+      return pair.value === value; 
+    });
+    return match && match.key;
+  },
+  
   merge: function(hash) {
     return $H(hash).inject(this, function(mergedHash, pair) {
       mergedHash[pair.key] = pair.value;

test/unit/hash.html

@@ -89,7 +89,19 @@
         $H(Fixtures.functions).values().map(function(i){ return typeof i }));
       assertEqual(9, $H(Fixtures.functions).quad(3));
       assertEqual(6, $H(Fixtures.functions).plus(3));
-    }},  
+    }},
+    
+    testIndex: function(){ with(this) {
+      assertUndefined($H().index('foo'));
+      
+      assert('a', $H(Fixtures.one).index('A#'));
+      assert('a', $H(Fixtures.many).index('A'));
+      assertUndefined($H(Fixtures.many).index('Z'))
+    
+      var hash = $H({a:1,b:'2',c:1});
+      assert(['a','c'].include(hash.index(1)));
+      assertUndefined(hash.index('1'));
+    }},
       
     testMerge: function(){ with(this) {
       assertHashEqual(Fixtures.many, $H(Fixtures.many).merge());