Merge pull request #614 from mastermatt/bufix-shuffle-last-element

Bugfix random.shuffle last element.

2 files changed, 23 insertions, 3 deletions

diff --git a/lib/helpers.js b/lib/helpers.js
index f2b12da6..4100c766 100644
--- a/lib/helpers.js
+++ b/lib/helpers.js
@@ -194,17 +194,24 @@ var Helpers = function (faker) {
    };
 
   /**
-   * takes an array and returns it randomized
+   * takes an array and randomizes it in place then returns it
+   * 
+   * uses the modern version of the Fisher–Yates algorithm
    *
    * @method faker.helpers.shuffle
    * @param {array} o
    */
   self.shuffle = function (o) {
       if (typeof o === 'undefined' || o.length === 0) {
-        return [];
+        return o || [];
       }
       o = o || ["a", "b", "c"];
-      for (var j, x, i = o.length-1; i; j = faker.random.number(i), x = o[--i], o[i] = o[j], o[j] = x);
+      for (var x, j, i = o.length - 1; i > 0; --i) {
+        j = faker.random.number(i);
+        x = o[i];
+        o[i] = o[j];
+        o[j] = x;
+      }
       return o;
   };
 
diff --git a/test/helpers.unit.js b/test/helpers.unit.js
index 5c8b31d5..f08be413 100644
--- a/test/helpers.unit.js
+++ b/test/helpers.unit.js
@@ -43,6 +43,19 @@ describe("helpers.js", function () {
             var shuffled = faker.helpers.shuffle([]);
             assert.ok(shuffled.length === 0);
         });
+
+        it("mutates the input array in place", function () {
+            var input = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"];
+            var shuffled = faker.helpers.shuffle(input);
+            assert.deepEqual(shuffled, input);
+        });
+
+        it("all items shuffled as expected when seeded", function () {
+            var input = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j"];
+            faker.seed(100);
+            var shuffled = faker.helpers.shuffle(input);
+            assert.deepEqual(shuffled, ["b", "e", "a", "d", "j", "i", "h", "c", "g", "f"]);
+        });
     });
 
     describe("slugify()", function () {