code: function(num) {
        var result = '', str = this;
        if(!isNumber(num) || num < 1) return '';
        while (num) {
          if (num & 1) {
            result += str;
          }
          if (num >>= 1) {
            str += str;
          }
        }
        return result;
      }
docs: *
  @method repeat([num] = 0)
  @returns String
  @short Returns the string repeated [num] times.
  @example
  
  'jumpy'.repeat(2) -> 'jumpyjumpy'
  'a'.repeat(5)     -> 'aaaaa'
  'a'.repeat(0)     -> ''
  
  *