Fast String.prototype.repeat

dbravender · Oct 3, 2012 · b094765 · b094765
1 parent 3147b81
commit b094765
Showing 1 changed file with 13 additions and 8 deletions.
diff --git a/lib/string.js b/lib/string.js
@@ -753,17 +753,23 @@
      *
      *   'jumpy'.repeat(2) -> 'jumpyjumpy'
      *   'a'.repeat(5)     -> 'aaaaa'
+     *   'a'.repeat(0)     -> ''
      *
      ***/
     'repeat': function(num) {
-      var str = '', i = 0;
-      if(isNumber(num) && num > 0) {
-        while(i < num) {
-          str += this;
-          i++;
-        }
+      if(!isNumber(num) || num < 1)return "";
+
+      var result = '', self = this;
+
+      while (num) {
+        if (num & 1)
+          result += self;
+
+        if (num >>= 1)
+          self += self;
       }
-      return str;
+
+      return result;
     },
 
     /***
@@ -851,7 +857,6 @@
       });
       return context;
     }
-
   });