improve string/repeat performance

based on: http://stackoverflow.com/questions/202605/repeat-string-javascript
Performance tests: http://jsfiddle.net/disfated/GejWV/

closes mout#164

.gitignore

@@ -6,6 +6,7 @@
 .project
 .settings/
 .livereload
+.idea
 
 .DS_Store?
 ehthumbs.db

CHANGELOG.md

@@ -3,7 +3,7 @@ mout changelog
 
 next
 ----
-
+ - improve `string/repeat` performance.
  - add `function/constant`
 
 v0.8.0 (2013/11/22)

src/string/repeat.js

@@ -1,11 +1,23 @@
-define(['../lang/toString'], function(toString){
+define(['../lang/toString', '../number/toInt'], function(toString, toInt){
 
     /**
      * Repeat string n times
      */
      function repeat(str, n){
+         var result = '';
          str = toString(str);
-         return (new Array(n + 1)).join(str);
+         n = toInt(n);
+        if (n < 1) {
+            return '';
+        }
+        while (n > 0) {
+            if (n % 2) {
+                result += str;
+            }
+            n = Math.floor(n / 2);
+            str += str;
+        }
+        return result;
      }
 
      return repeat;

tests/spec/string/spec-repeat.js

@@ -18,7 +18,9 @@ define(['mout/string/repeat'], function (repeat) {
         it('should tread undefined as empty string', function(){
             expect( repeat(void 0, 1) ).toEqual('');
         });
-
+        it('should treat "ab" as not a number', function(){
+            expect( repeat('a','ab') ).toEqual('');
+        });
     });
 
 });