Understanding JSON: the 3 minute lesson

Source

What does it stand for?
JavaScript Object Notation.

And what does that mean?
JSON is a syntax for passing around objects that contain name/value pairs, arrays and other objects.

Here's a tiny scrap of JSON:

{"skillz": {
"web":[
{"name": "html",
"years": "5"
},
{"name": "css",
"years": "3"
}],
"database":[
{"name": "sql",
"years": "7"
}]
}}

You got that? So you'd recognise some JSON if you saw it now? Basically:

Squiggles, Squares, Colons and Commas
Squiggly brackets act as 'containers'
Square brackets holds arrays
Names and values are separated by a colon.
Array elements are separated by commas

JSON is like XML because:
They are both 'self-describing' meaning that values are named, and thus 'human readable'
Both are hierarchical. (i.e. You can have values within values.)
Both can be parsed and used by lots of programming languages
Both can be passed around using AJAX (i.e. httpWebRequest)

JSON is UNlike XML because:
XML uses angle brackets, with a tag name at the start and end of an element: JSON uses squiggly brackets with the name only at the beginning of the element.
JSON is less verbose so it's definitely quicker for humans to write, and probably quicker for us to read.
JSON can be parsed trivially using the eval() procedure in JavaScript
JSON includes arrays {where each element doesn't have a name of its own}
In XML you can use any name you want for an element, in JSON you can't use reserved words from javascript
But Why? What's good about it?
When you're writing ajax stuff, if you use JSON, then you avoid hand-writing xml. This is quicker.

Again, when you're writing ajax stuff, which looks easier? the XML approach or the JSON approach:

The XML approach:
bring back an XML document
loop through it, extracting values from it
do something with those values, etc,
versus
The JSON approach:
bring back a JSON string.
'eval' the JSON
So this is Object-Oriented huh?
Nah, not strictly.

JSON provides a nice encapsulation technique, that you can use for separating values and functions out, but it doesn't provide anything inheritence, polymorphism, interfaces, or OO goodness like that.

And it's just for the client-side right?
Yes and no. On the server-side you can easily serialize/deserialize your objects to/from JSON. For .net programmers you can use libraries like Json.net to do this automatically for you (using reflection i assume), or you can generate your own custom code to perform it even faster on a case by case basis.