JSON Interview Questions & Answers

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JSON Interview Questions & Answers

  1. Mention what is JSON?

JSON is a simple data exchange format.  JSON means JavaScript Object Notation; it is language and platform independent.
2.  Explain what is JSON objects?

An object can be defined as an unordered set of name/value pairs.  An object in JSON starts with {left brace} and finish or ends with {right brace}.  Every name is followed by: (colon) and the name/value pairs are parted by, (comma).

3.  Explain how to transform JSON text to a JavaScript object?

One of the common use of JSON is to collect JSON data from a web server as a file or HTTP request, and convert the JSON data to a JavaScript, ant then it avails the data in a web page.

4. Mention what is the rule for JSON syntax rules? Give an example of JSON object?

JSON syntax is a set of the JavaScript object notation syntax.

  • Data is in name/value pairs
  • Data is separated by comma
  • Curly brackets hold objects
  • Square bracket holds arrays

JSON with Ajax

AJAX is Asynchronous JavaScript and XML, which is used on the client side as a group of interrelated web development techniques, in order to create asynchronous web applications. According to the AJAX model, web applications can send and retrieve data from a server asynchronously without interfering with the display and the behavior of the existing page.

Many developers use JSON to pass AJAX updates between the client and the server. Websites updating live sports scores can be considered as an example of AJAX. If these scores have to be updated on the website, then they must be stored on the server so that the webpage can retrieve the score when it is required. This is where we can make use of JSON formatted data.

Any data that is updated using AJAX can be stored using the JSON format on the web server. AJAX is used so that javascript can retrieve these JSON files when necessary, parse them, and perform one of the following operations −

  • Store the parsed values in the variables for further processing before displaying them on the webpage.
  • It directly assigns the data to the DOM elements in the webpage, so that they are displayed on the website.

–    Example

The following code shows JSON with AJAX. Save it as ajax.htm file. Here the loading function loadJSON() is used asynchronously to upload JSON data.

<html>

<head>

<metacontent=”text/html; charset = ISO-8859-1″http-equiv=”content-type”>

function loadJSON(){

var data_file=”http://www.tutorialspoint.com/json/data.json&#8221;;

var http_request =newXMLHttpRequest();

try{

// Opera 8.0+, Firefox, Chrome, Safari

http_request =newXMLHttpRequest();

}catch(e){

// Internet Explorer Browsers{

try{

http_request =newActiveXObject(“Microsoft.XMLHTTP”);

}catch(e){

// Something went wrong

alert(“Your browser broke!”);

returnfalse;

}

}

}

http_request.onreadystatechange =function(){

if(http_request.readyState ==4){

// Javascript function JSON.parse to parse JSON data

var jsonObj = JSON.parse(http_request.responseText);

// jsonObj variable now contains the data structure and can

// be accessed as jsonObj.name and jsonObj.country.

document.getElementById(“Name”).innerHTML = jsonObj.name;

document.getElementById(“Country”).innerHTML = jsonObj.country;

}

}

http_request.open(“GET”, data_file,true);

http_request.send();

}

<title>tutorialspoint.com JSON</title>

</head>

 

<body>

<h1>Cricketer Details</h1>

<tableclass=”src”>

<tr><th>Name</th><th>Country</th></tr>

<tr><td>Sachin

</td>

<td>India

</td></tr>

</table>

Update Details

</body>

</html>

Given below is the input file data.json, having data in JSON format which will be uploaded asynchronously when we click the Update Detail button. This file is being kept in http://www.tutorialspoint.com/json/

{“name”: “Brett”, “country”: “Australia”}

The above HTML code will generate the following screen, where you can check AJAX in action –

Cricketer Details

Name Country
Sachin India

When you click on the Update Detail button, you should get a result something as follows. You can try JSON with AJAX yourself, provided your browser supports Javascript.

Cricketer Details

Name Country
Brett Australia