_.groupsOf

index.html

@@ -215,6 +215,7 @@
       <li>- <a href="#initial">initial</a></li>
       <li>- <a href="#last">last</a></li>
       <li>- <a href="#rest">rest</a></li>
+      <li>- <a href="#chunk">chunk</a></li>
       <li>- <a href="#compact">compact</a></li>
       <li>- <a href="#flatten">flatten</a></li>
       <li>- <a href="#without">without</a></li>
@@ -691,6 +692,21 @@ <h2 id="arrays">Array Functions</h2>
       <pre>
 _.rest([5, 4, 3, 2, 1]);
 =&gt; [4, 3, 2, 1]
+</pre>
+
+      <p id="chunk">
+        <b class="header">chunk</b><code>_.chunk(array, n)</code>
+        <br />
+        Returns an array of arrays in <b>chunks</b> of size <b>n</b> with the last
+        group contining the remaining elements if <b>n</b> does not evenly divide the
+        length of <b>array</b>.
+      </p>
+      <pre>
+_.chunk([1, 2, 3, 4, 5, 6], 3);
+=&gt; [[1, 2, 3], [4, 5, 6]]
+
+_.chunk([1, 2, 3, 4, 5, 6], 4);
+=&gt; [[1, 2, 3, 4], [5, 6]]
 </pre>
 
       <p id="compact">

test/arrays.js

@@ -27,6 +27,21 @@ $(document).ready(function() {
     equal(_.flatten(result).join(','), '2,3,2,3', 'works well with _.map');
   });
 
+  test("arrays: chunk", function() {
+    var list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
+
+    var chunks = _.chunk(list, 5);
+    equal(chunks[0].join(',') + chunks[1].join(','),
+      '1,2,3,4,56,7,8,9,0',
+      'can chunk by a value that evenly divides the input array\'s length');
+
+    chunks = _.chunk(list, 3)
+    equal(chunks[0].join(',') + chunks[1].join(',') + chunks[2].join(',') + chunks[3].join(','),
+      '1,2,34,5,67,8,90',
+      'can chunk by a value that does not evenly divide the input array\'s length');
+  });
+
+
   test("arrays: initial", function() {
     equal(_.initial([1,2,3,4,5]).join(", "), "1, 2, 3, 4", 'working initial()');
     equal(_.initial([1,2,3,4],2).join(", "), "1, 2", 'initial can take an index');

underscore.js

@@ -378,6 +378,16 @@
     return slice.call(array, (index == null) || guard ? 1 : index);
   };
 
+  // Return an array of arrays of length at least n
+  _.chunk = function(array, n) {
+    var chunks = [];
+    var numChunks = Math.ceil(array.length / n);
+    for(var i = 0; i < numChunks; i++) {
+      chunks.push(array.slice(i * n, i * n + n));
+    }
+    return chunks;
+  }
+
   // Trim out all falsy values from an array.
   _.compact = function(array) {
     return _.filter(array, function(value){ return !!value; });