JSON

JSON - JavaScript Object Notation

It is a syntax for storing and exchanging data.
It is text, written with JavaScript object notation.

What is JSON?
- lightweight data-interchange format
- "self-describing" and easy to understand
- language independent *

Why use JSON?
JSON format is text only
Easily be sent to and from a server
Used as a data format by any programming language
JavaScript has a built in function to convert
-- JSON.parse()
-- JSON.stringify()

Why JSON?

1. Sending Data to Server
var myObj= { "name":“Sam", "age":21, "city":“Colombo" };
var myJSON = JSON.stringify(myObj);

2. Receiving Data from Server
var myJSON = { "name":“Sam", "age":21, "city":“Colombo" };
var myObj = JSON.parse(myJSON);

JSON Syntax Rules
JSON syntax is derived from JavaScript object notation syntax:
-- Data is in name/value pairs
-- Data is separated by commas
-- Curly braces hold objects
-- Square brackets hold arrays

Storing Data

     1.   Storing data:
                 myObj = { "name":"Shanu", "age":20, "city":"Jaffna" };
                 myJSON = JSON.stringify(myObj);
                 localStorage.setItem("testJSON", myJSON);

    2.     Retrieving data:
                 text = localStorage.getItem("testJSON");
                 obj = JSON.parse(text);
                 document.getElementById("demo").innerHTML = obj.name;

JSON Values
In JSON,values must be one of the following data types:
-- string
-- a number
-- an object (JSON object)
-- an array
-- a boolean
-- null
Eg:

      { "name":"Shanu" }

In JavaScript values can be all of the above, plus any other valid JavaScript expression, including:
-- a function
-- a date
-- undefined

Eg:

   { name:'Shanu' }

JSON 

--- Strings
{

 "name":"Shanu" 

}

--- Numbers
{

 "age":20

 }

--- Objects
{
"employee":{ "name":"Shanu", "age":20, "city":"Jaffna" }
}
--- Arrays
{
"employees":[ "Vimal", "Kala", "Mala" ]
}

--- Booleans
{

 "sale":true

 }
--- null
{

 "middlename":null

 }