--- a/core-javascript/objects.rst	Wed Oct 19 13:46:07 2011 +0100
+++ b/core-javascript/objects.rst	Wed Oct 19 17:02:48 2011 +0100
@@ -3,3 +3,175 @@
 
 JavaScript has objects and is object-oriented, but in an unusual way
 (more on that later).
+
+
+Simple objects
+--------------
+
+Simple objects are like dictionaries or hashes in other languages.
+They support key-value storage and access to attributes.  Here's how
+to create a simple object.
+
+.. code-block:: javascript
+
+   js> obj = {}
+   [object Object]
+
+   js> typeof obj
+   object
+
+We can store attribute values in a simple object (or any object in the
+doc:`object-tree`).
+
+.. code-block:: javascript
+
+   js> obj.s = 'hi'
+   hi
+   js> obj.i = 10
+   10
+
+We can get these values back again.
+
+.. code-block:: javascript
+
+   js> obj.s === 'hi'
+   true
+   js> obj.i == 10
+   true
+
+
+Missing attributes
+------------------
+
+It's not an error to ask for something that's not there.  We get
+undefined.
+
+.. code-block:: javascript
+
+   js> obj.dne === undefined
+   true
+
+We still get undefined if we set the value to undefined.
+
+.. code-block:: javascript
+
+   js> obj.undef = undefined
+   undefined
+   js> obj.dne === undefined
+   true
+
+You can use null to signal that there is a value, but that it is None.
+
+.. code-block:: javascript
+
+   js> obj.none = null
+   null
+   js> obj.none === null
+   true
+
+
+hasOwnProperty
+--------------
+
+You can use hasOwnProperty to help figure out why an object has an
+undefined attribute.  It's also useful when inspecting the
+doc::`object-tree`.  Often, however, it's better to write your code so
+you don't need to do this (for example by using null).
+
+.. code-block:: javascript
+
+   js> obj.hasOwnProperty('dne')
+   false
+   js> obj.hasOwnProperty('undef')
+   true
+   js> obj.hasOwnProperty('none')
+   true
+
+
+Object literals
+---------------
+
+You can create a simple object by placing key-value pairs in the curly
+braces.
+
+.. code-block:: javascript
+
+   js> someone = {
+     >     'name': 'Joe Doe',
+     >     'age': 43
+     > }
+   [object Object]
+
+   js> someone.age
+   43
+
+Take care *not* to put a trailing semicolon in the object literal.  It
+will work in Firefox but not in Internet Explorer.
+
+
+Arrays
+------
+
+An array is a list of items.  You can put anything is as a value for
+the list.  Use square brackets to create an array.
+
+.. code-block:: javascript
+
+   js> array = []
+
+Arrays expand to accomodate the data you store in them.  You can even
+leave gaps.
+
+.. code-block:: javascript
+
+   js> array[0] = 'zero'
+   zero
+   js> array[3] = 'three'
+   three
+
+An array turned into a string consists of the string on its entries
+joined by commas.
+
+.. code-block:: javascript
+
+   js> array
+   zero,,,three
+   js> array[1] === undefined
+   true
+
+
+Array literals
+--------------
+
+As with simple objects, simply place the values between the square
+brackets, separated by commas.
+
+.. code-block:: javascript
+
+   js> seasons = ['spring', 'summer', 'autumn', 'winter']
+   spring,summer,autumn,winter
+
+
+As with simple objects, beware of trailing commas and missing entries.
+This will work in some browsers and not others.
+
+
+JSON
+----
+
+`JSON <http://www.json.org/>`_,stands for JavaScript Simple Object
+Notation.  It is very much one of the best parts of JavaScript.  It is
+`the fat-free alternative to XML <http://www.json.org/xml.html>`_, and
+is widely used in AJAX (instead of XML).  JSON objects are object and
+array literals constructed using only simple objects, arrays, strings,
+true, false and null.
+
+If your code accepts JSON objects then it will be a lot easier to use
+it with AJAX or otherwise integrate it with other systems.
+
+Many programming languages have JSON libraries.  You don't have to use
+JavaScript to use JSON.
+
+To provide standards, there are rules on how to write a JSON objects.
+Many applications and programming languages will generate valid JSON
+for you.  I find YAML a convenient way of authoring JSON data.