4 files changed, 42 insertions, 0 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index cb7a782704..a513cd570b 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Document Enumerable and Hash #to_json.  #9970 [Chu Yeow]
+
 * Hash#to_xml handles symbol values.  #9954 [Assaf]
 
 * Hash#symbolize_keys behaves well with integer keys.  #9890 [PotatoSalad]
diff --git a/activesupport/lib/active_support/json/encoders/enumerable.rb b/activesupport/lib/active_support/json/encoders/enumerable.rb
index d180049663..720fd88f90 100644
--- a/activesupport/lib/active_support/json/encoders/enumerable.rb
+++ b/activesupport/lib/active_support/json/encoders/enumerable.rb
@@ -1,4 +1,11 @@
 module Enumerable
+  # Returns a JSON string representing the enumerable. Any +options+
+  # given will be passed on to its elements. For example:
+  #
+  # users = User.find(:all)
+  # users.to_json(:only => :name)
+  #
+  # will pass the <tt>:only => :name</tt> option to each user.
   def to_json(options = {}) #:nodoc:
     "[#{map { |value| ActiveSupport::JSON.encode(value, options) } * ', '}]"
   end
diff --git a/activesupport/lib/active_support/json/encoders/hash.rb b/activesupport/lib/active_support/json/encoders/hash.rb
index 14b91a76a1..774803d64f 100644
--- a/activesupport/lib/active_support/json/encoders/hash.rb
+++ b/activesupport/lib/active_support/json/encoders/hash.rb
@@ -1,4 +1,36 @@
 class Hash
+  # Returns a JSON string representing the hash.
+  #
+  # Without any +options+, the returned JSON string will include all
+  # the hash keys. For example:
+  #
+  #   { :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json
+  #
+  #   {"name": "Konata Izumi", 1: 2, "age": 16}
+  #
+  # The keys in the JSON string are unordered due to the nature of hashes.
+  #
+  # The <tt>:only</tt> and <tt>:except</tt> options can be used to limit the
+  # attributes included, and will accept 1 or more hash keys to include/exclude.
+  #
+  #   { :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json(:only => [:name, 'age'])
+  #
+  #   {"name": "Konata Izumi", "age": 16}
+  #
+  #   { :name => "Konata Izumi", 'age' => 16, 1 => 2 }.to_json(:except => 1)
+  #
+  #   {"name": "Konata Izumi", "age": 16}
+  #
+  # The +options+ also filter down to any hash values. This is particularly
+  # useful for converting hashes containing ActiveRecord objects or any object
+  # that responds to options in their <tt>to_json</tt> method. For example:
+  #
+  #   users = User.find(:all)
+  #   { :users => users, :count => users.size }.to_json(:include => :posts)
+  #
+  # would pass the <tt>:include => :posts</tt> option to <tt>users</tt>,
+  # allowing the posts association in the User model to be converted to JSON
+  # as well.
   def to_json(options = {}) #:nodoc:
     hash_keys = self.keys
 
diff --git a/activesupport/test/json/encoding_test.rb b/activesupport/test/json/encoding_test.rb
index c42832b371..923f4b8396 100644
--- a/activesupport/test/json/encoding_test.rb
+++ b/activesupport/test/json/encoding_test.rb
@@ -45,6 +45,7 @@ class TestJSONEncoding < Test::Unit::TestCase
     assert_equal %({\"a\": \"b\"}), { :a => :b }.to_json
     assert_equal %({\"a\": 1}), { 'a' => 1  }.to_json
     assert_equal %({\"a\": [1, 2]}), { 'a' => [1,2] }.to_json
+    assert_equal %({1: 2}), { 1 => 2 }.to_json
 
     sorted_json = '{' + {:a => :b, :c => :d}.to_json[1..-2].split(', ').sort.join(', ') + '}'
     assert_equal %({\"a\": \"b\", \"c\": \"d\"}), sorted_json