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A gem for joining items in arrays together into grammatically correct series, such as "a, b and c".
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A gem for joining items in arrays together into grammatically correct series, such as "a, b and c".

SeriesJoiner extends the Array class with a join_as_series() method which is similar to the built-in join() method. However, join_as_series() allows for custom delimiters and conjunctions.


Run the following (perhaps as sudo):

gem install series_joiner

Bundler Configuration

Add the following to your Gemfile:

gem 'series_joiner'


join_as_series() accepts the following options:

:delimiter       # inserted between items, except for the final two (default => ', ')
:final_delimiter # inserted between the final two items (if > 2), but before the conjunction (default => '')
:conjunction     # inserted between the final two items (default => ' and ')

By default, items are joined as follows:

['a'].join_as_series #=> 'a'

['a', 'b'].join_as_series #=> 'a and b'

['a', 'b', 'c'].join_as_series #=> 'a, b and c'

['a', 'b', 'c', 'd'].join_as_series #=> 'a, b, c and d'

Here are some examples using custom delimiters and/or conjunctions:

['a', 'b', 'c'].join_as_series(:delimiter => '; ') #=> 'a; b and c'

['a', 'b', 'c'].join_as_series(:conjunction => ' or ') #=> 'a, b or c'

['a', 'b', 'c'].join_as_series(:delimiter => '; ', :conjunction => '; or, ') #=> 'a; b; or, c'

The use of the serial comma (i.e. the final comma sometimes used before the conjunction) is much debated in grammar circles ( And who doesn't enjoy a rousing debate about grammar? Don't answer that. Anyway, SeriesJoiner does not use the serial comma by default. If you prefer to use it, just set the :final_delimiter option to ',':

['a', 'b', 'c'].join_as_series(:final_delimiter => ',') #=> 'a, b, and c'

I18n Support

If you're using SeriesJoiner in a project with I18n support, include the following translations for your locales:

      default_delimiter: ', '
      default_final_delimiter: ''
      default_conjunction: ' and '


This gem uses rspec for testing. To test:

rake spec


This gem's join_as_series() method may be compared with the similar to_sentence() method implemented in ActiveSupport ( There are several differences:

  • to_sentence() is part of ActiveSupport, while join_as_series is independent;
  • to_sentence() implements the serial comma (see definition above) by default, while join_as_series() does not; and,
  • to_sentence() requires two options (:two_words_connector and :last_word_connector) to override a conjunction, instead of the one (:conjunction) required by join_as_series().


Copyright (c) 2011 Cerebris Corporation. This is free software released under the MIT License (see MIT-LICENSE for details).

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