To use the push function of an Array your var needs to be an Array.

Change data{"name":"ananta","age":"15"} to following:

var data = [
    { 
        "name": "ananta",
        "age": "15",
        "country": "Atlanta"
    }
];

data.push({"name": "Tony Montana", "age": "99"});

data.push({"country": "IN"});

..

The containing Array Items will be typeof Object and you can do following:

var text = "You are " + data[0]->age + " old and come from " + data[0]->country;

Notice: Try to be consistent. In my example, one array contained object properties name and age while the other only contains country. If I iterate this with for or forEach then I can't always check for one property, because my example contains Items that changing.

Perfect would be: data.push({ "name": "Max", "age": "5", "country": "Anywhere" } );

So you can iterate and always can get the properties, even if they are empty, null or undefined.

edit

Cool stuff to know:

var array = new Array();

is similar to:

var array = [];

Also:

var object = new Object();

is similar to:

var object = {};

You also can combine them:

var objectArray = [{}, {}, {}];

Your data variable contains an object, not an array, and objects do not have the push function as the error states. To do what you need you can do this:

data.country = 'IN';

Or

data['country'] = 'IN';

Also make sure that the name of the variable is not some kind of a language keyword. For instance, the following produces the same type of error:

var history = [];
history.push("what a mess");

replacing it for:

var history123 = [];
history123.push("pray for a better language");

works as expected.