What is JSON

What is JSON
JSON stands for JavaScript Object Notation. JSON is a lightweight data-interchange format. JSON is an easier-to-use alternative to XML. 

Creating a JSON object : Employee data can be stored in a JSON object as shown below. 

var employeeJSON = {
    "firstName": "Todd",
    "lastName": "Grover",
    "gender": "Male",
    "salary": 50000
};

1. employeeJSON is a JSON object
2. In the curly braces we include the "name": "value" pairs, separated by commas
3. The name and value of a property are separated using a colon (:)
4. You can declare any number of properties

If you want to represent the same data using XML, you may have XML that would look as shown below.
<Employee>
  <firstName>Todd</firstName>
  <lastName>Grover</lastName>
  <gender>Male</gender>
  <salary>50000</salary>
</Employee>

Reading data from the JSON object : To read data from the JSON object, use the property names.
var firstName = employeeJSON.firstName;

Creating and accessing data from a JSON object
<html>
<head>
    <title></title>
    <script src="jquery-1.11.2.js"></script>
    <script type="text/javascript">
        $(document).ready(function () {

            // Creating a JSON object
            var employeeJSON = {
                "firstName": "Todd",
                "lastName": "Grover",
                "gender": "Male",
                "salary": 50000
            };

            // Accessing data from a JSON object
            var result = '';
            result += 'First Name = ' + employeeJSON.firstName + '<br/>';
            result += 'Last Name = ' + employeeJSON.lastName + '<br/>';
            result += 'Gender = ' + employeeJSON.gender + '<br/>';
            result += 'Salary = ' + employeeJSON.salary + '<br/>';

            $('#resultDiv').html(result);
        });
    </script>
</head>
<body style="font-family:Arial">
    <div id="resultDiv"></div>
</body>
</html>

Output :  
creating json object in javascript 

JSON Arrays : What if you want to store more than one employee data in the JSON object. This is when JSON arrays can be used. A JSON array can contain multiple objects.

To create a JSON array 
1. Wrap the objects in square brackets
2. Each object must be separated with a comma

Creating a JSON array 
var employeesJSON = [
{
    "firstName": "Todd",
    "lastName": "Grover",
    "gender": "Male",
    "salary": 50000
},
{
    "firstName": "Sara",
    "lastName": "Baker",
    "gender": "Female",
    "salary": 40000
}];

Reading from a JSON array : To access the employee objects in the JSON array, use the object's index position.

Retrieves the lastName of first employee object in the JSON array
var result = employeesJSON[0].lastName;

Retrieves the fistName of second employee object in the JSON array
var result = employeesJSON[1].firstName;

Nested JSON object : You can also store multiple employees in the JSON object by nesting them.

Nested JSON object example : 

var employeesJSON = {
    "Todd": {
        "firstName": "Todd",
        "lastName": "Grover",
        "gender": "Male",
        "salary": 50000
    },
    "Sara": {
        "firstName": "Sara",
        "lastName": "Baker",
        "gender": "Female",
        "salary": 40000
    }
};

Retrieves the gender of employee Todd
var result = employeesJSON.Todd.gender;

Retrieves the salary of employee Sara
var result = employeesJSON.Sara.salary;

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