JSON Interview Questions

JSON (JavaScript Object Notation) is a data storage and communication format based on a key-value pair of JavaScript object literals. It is a lightweight text-based open standard designed for human-readable data interchange.

Read Best JSON Interview Questions and Answers 2018.

#1 List some benefits of JSON over XML?

  • It is faster and lighter than XML as on the wire data format
  • XML data is typeless while JSON objects are typed
  • JSON types: Number, Array, Boolean, String
  • XML data are all string
  • Data is readily available as JSON object is in your JavaScript
  • Fetching values is as simple as reading from an object property in your JavaScript code

#2 How do you decode a JSON string?

Use JSON.parse method to decode a JSON string into a Javascript object.

#3 List types Natively supported by JSON?

JSON supports Objects, Arrays, Primitives (strings, numbers, boolean values (true/false), null) data types.

#4 What does hasOwnProperty method do?

It returns true if the property was set on an actual object rather than inherited.

#5 What does $.parseJSON() do ?

$.parseJSON() takes a well-formed JSON string and returns the resulting JavaScript value.

#6 What are natively supported JSON types?

Following data types are natively supported in JSON.
  • Numbers: Integer, float or Double
  • String: string of Unicode characters, must be rapped into double quotes “”
  • Boolean: True or false
  • Array: ordered list of 0 or more values
  • Objects : An unordered collection key/ value pairs
  • Null: An Empty value

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#7 How to delete an index from JSON Obj?

Deleting an Element from JSON Obj
var exjson = {'key':'value'};
delete exjson['key'];

#8 Who is the Father of JSON and What is the scripting language JSON is based on?

Douglas Crockford called as the Father of JSON. JSON is based on ECMAScript.

#9 What is JSON? For what is used for?

JSON (JavaScript Object Notation) is a data storage and communication format based on key-value pair of JavaScript object literals. It is a lightweight text-based open standard designed for human-readable data interchange which is derived from the JavaScript programming language for representing simple data structures and associative arrays, called objects.

In JSON

  • all property names are surrounded by double quotes.
  • values are restricted to simple data: no function calls, variables, comments, or computations.

JSON is used for communication between javascript and serverside technologies.

#10 What are different ways to create objects?

You can create Object by
  • object literals
  • Object.create
  • constructors

#11 What is JSON-RPC? List some Features of JSON-RPC-Java

JSON-RPC: JSON-RPC is a simple remote procedure call protocol similar to XML-RPC although it uses the lightweight JSON format instead of XML.

JSON-RPC-Java is a Java implementation of the JSON-RPC protocol.Below is list of some of its features

  • Dynamically call server-side Java methods from JavaScript DHTML web applications. No Page reloading.
  • Asynchronous communications.
  • Transparently maps Java objects to JavaScript objects.
  • Lightweight protocol similar to XML-RPC although much faster.
  • Leverages J2EE security model with session specific exporting of objects.
  • Supports Internet Explorer, Mozilla, Firefox, Safari, Opera, and Konqueror.

#12 What is the difference between JSON and JSONP?

  • JSON: JSON is a simple data format used for communication medium between different systems
  • JSONP: It is a methodology for using that format with cross-domain ajax requests while not being affected by same origin policy issue.

#13 What is the default value of a constructor’s prototype?

A plain, empty object that derives from Object.prototype is the default value of a constructor’s prototype

#14 How to convert Javascript objects into JSON?

JSON.stringify(value); is used to convert Javascript objects into JSON.

Example Usage:

    var obj={"website":"Onlineinterviewquestions"};
    JSON.stringify(obj); // '{"website":"Onlineinterviewquestions"}'

#15 What JS-specific properties are skipped by JSON.stringify method?

Following JS-specific properties are skipped by JSON.stringify method
  • Function properties (methods).
  • Symbolic properties.
  • Properties that store undefined.
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