added an isEmpty function that works on arrays and objects

index.html

@@ -192,7 +192,8 @@ _(lyrics).chain()
       <b>Objects</b>
       <br />
       <span class="methods"><a href="#keys">keys</a>, <a href="#values">values</a>, 
-      <a href="#extend">extend</a>, <a href="#clone">clone</a>, <a href="#isEqual">isEqual</a>, <a href="#isElement">isElement</a>, 
+      <a href="#extend">extend</a>, <a href="#clone">clone</a>, 
+      <a href="#isEqual">isEqual</a>, <a href="#isEmpty">isEmpty</a>, <a href="#isElement">isElement</a>, 
       <a href="#isArray">isArray</a>, <a href="#isFunction">isFunction</a>, <a href="#isUndefined">isUndefined</a>
       </span>
     </p>
@@ -710,6 +711,18 @@ moe == clone;
 =&gt; false
 _.isEqual(moe, clone);
 =&gt; true
+</pre>
+
+      <p id="isEmpty">
+        <b class="header">isEmpty</b><code>_.isEmpty(object)</code>
+        <br />
+        Returns <i>true</i> if <b>object</b> contains no values.
+      </p>
+      <pre>
+_.isEmpty([1, 2, 3]);
+=&gt; false
+_.isEmpty({});
+=&gt; true
 </pre>
 
       <p id="isElement">

test/objects.js

@@ -36,6 +36,17 @@ $(document).ready(function() {
     ok(_(moe).isEqual(clone), 'OO-style deep equality works');
   });
   
+  test("objects: isEmpty", function() {
+    ok(!_([1]).isEmpty(), '[1] is not empty');
+    ok(_.isEmpty([]), '[] is empty');
+    ok(!_.isEmpty({one : 1}), '{one : 1} is not empty');
+    ok(_.isEmpty({}), '{} is empty');
+    
+    var obj = {one : 1};
+    delete obj.one;
+    ok(_.isEmpty(obj), 'deleting all the keys from an object empties it');
+  });
+  
   test("objects: isElement", function() {
     ok(!_.isElement('div'), 'strings are not dom elements');
     ok(_.isElement($('html')[0]), 'the html tag is a DOM element');

test/utility.js

@@ -25,7 +25,7 @@ $(document).ready(function() {
     var expected = ["all", "any", "bind", "bindAll", "clone", "compact", "compose", 
     "defer", "delay", "detect", "each", "every", "extend", "filter", "first", 
     "flatten", "foldl", "foldr", "forEach", "functions", "identity", "include", 
-    "indexOf", "inject", "intersect", "invoke", "isArray", "isElement", "isEqual", 
+    "indexOf", "inject", "intersect", "invoke", "isArray", "isElement", "isEmpty", "isEqual", 
     "isFunction", "isUndefined", "keys", "last", "lastIndexOf", "map", "max", 
     "methods", "min", "pluck", "reduce", "reduceRight", "reject", "select", 
     "size", "some", "sortBy", "sortedIndex", "template", "toArray", "uniq", 

underscore.js

@@ -146,9 +146,7 @@
     if (_.isArray(obj)) return _.indexOf(obj, target) != -1;
     var found = false;
     _.each(obj, function(value) {
-      if (found = value === target) {
-        throw '__break__';
-      }
+      if (found = value === target) throw '__break__';
     });
     return found;
   };
@@ -409,6 +407,11 @@
     return true;
   };
   
+  // Is a given array or object empty?
+  _.isEmpty = function(obj) {
+    return (_.isArray(obj) ? obj : _.values(obj)).length == 0;
+  };
+  
   // Is a given value a DOM element?
   _.isElement = function(obj) {
     return !!(obj && obj.nodeType == 1);