javascript interview questions and answers

 javascript interview questions and answers

today, Google and Facebook use JavaScript to build complex, desktop-like web applications. With the launch of Node.js, It has also become one of the most popular languages for building server-side software. Today, even the web isn’t big enough to contain JavaScript’s versatility. I believe that you are already aware of these facts and this has made you land on this JavaScript Interview Questions article. 

So, if you are planning to start your career in JavaScript and you wish to know the skills related to it, now is the right time to dive in, when the technology is in its blossoming state. JavaScript Interview Questions and our JavaScript training will provide you with in-depth knowledge and help you prepare for your interviews.

Q1. What is JavaScript?

JavaScript is a lightweight, interpreted programming language with object-oriented capabilities that allows you to build interactivity into otherwise static HTML pages. The general-purpose core of the language has been embedded in Netscape, Internet Explorer, and other web browsers.

Q2. What are the features of JavaScript?

Following are the features of JavaScript:

It is a lightweight, interpreted programming language.

It is designed for creating network-centric applications.

It is complementary to and integrated with Java.

It is an open and cross-platform scripting language.

Q3. What are the data types supported by JavaScript?

The data types supported by JavaScript are:

Undefined

Null

Boolean

String

Symbol

Number

Object

Q4. What are the features of JavaScript?

It is a lightweight, interpreted programming language.

It is designed for creating network-centric applications.

It is complementary to and integrated with Java.

It is an open and cross-platform scripting language.

Q5. Is JavaScript a case-sensitive language?

Yes, JavaScript is a case-sensitive language.  The language keywords, variables, function names, and any other identifiers must always be typed with a consistent capitalization of letters.

Following are the advantages of using JavaScript −

Less server interaction − You can validate user input before sending the page off to the server. This saves server traffic, which means less load on your server.

Immediate feedback to the visitors − They don’t have to wait for a page reload to see if they have forgotten to enter something.

Increased interactivity − You can create interfaces that react when the user hovers over them with a mouse or activates them via the keyboard.

Richer interfaces − You can use JavaScript to include such items as drag-and-drop components and sliders to give a Rich Interface to your site visitors.

Q7. How can you create an object in JavaScript?

JavaScript supports Object concepts very well. You can create an object using the object literal as follows −

var emp = {

name: "Daniel",

age: 23

};

Q8. What are the scopes of a variable in JavaScript?

The scope of a variable is the region of your program in which it is defined. JavaScript variable will have only two scopes.

• Global Variables − A global variable has a global scope which means it is visible everywhere in your JavaScript code.

• Local Variables − A local variable will be visible only within a function where it is defined. Function parameters are always local to that function.

Q9. What is the purpose of the ‘This’ operator in JavaScript?

The JavaScript this keyword refers to the object it belongs to. This has different values depending on where it is used. In a method, this refers to the owner object and in a function, this refers to the global object.