JavaScript Questions You Need To Know 
Tags: javascript, java, python, webdev
Published: 2021-05-27 10:36:25

JavaScript is one of the most used and best language currently. It solves the problem of of complex backend from java & C++ making the backend code less complex and faster.

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Let's See, **What Is JavaScript?**

JavaScript, also abbreviated as JS, is a high-level server-side programming language. JavaScript is widely used worldwide to build various web applications, App Backend and Database Programming as well. There are a lot of opportunities in this programming language for you. 

#**Now Let's See The Question-**


1.**What are JavaScript Data Types?**

This is one of the easiest question that you can get, but the interviewer expects you to give the most simplified answer you can give on this question.

*The answer should be -*
*Number
String
Boolean
Object
Undefined*

2.**Which is faster between JavaScript and an ASP script?**

JavaScript is both server-side language and client-side language [Node.js], and it doesn't assist webservers to execute on the other hand ASP is a server-side language and hence is always slower than JavaScript.

3.**Write the code for adding new elements dynamically?**

It is a very simple question, [Click here to get the answer.](https://linenewsletter.substack.com/p/write-the-code-for-adding-new-elements)

4.**What is the working of timers in JavaScript?**

Timers are used to execute a piece of code at a set time or repeat the code in a given interval. This is done by using the functions set Timeout, set Interval, & clear Interval.

5.**What is called Variable typing in JavaScript?**

Variable typing is used to assign a number to a variable. The same variable can be assigned to a string.

Code Example- 

*i = 10;*
*i = "string;"*

6. How closures work in JavaScript?

The closure is a locally declared variable related to a function that stays in memory when it has returned.

[Click Here To Get Code Example.](https://linenewsletter.substack.com/p/the-closure-is-a-locally-declared)

7.**What Boolean operators can be used in JavaScript?**

The 'And' Operator (&&), 'Or' Operator (||), and the 'Not' Operator (!) can be used in JavaScript.

*FACT - This question doesn't really feels important but* *actually it is.*

8.**What are the pros and cons object-oriented programming?**

##Pros :- 

*It’s easy to understand the basic concept of objects and easy to interpret the meaning of method calls. Object oriented programming tends to use an imperative style rather than a declarative style, which reads like a straight-forward set of instructions for the computer to follow.*

##Cons:-
*object oriented programming Typically depends on shared state. Objects and behaviors are typically tacked together on the same entity, which may be accessed at random by any number of functions with non-deterministic order, which may lead to undesirable behavior such as race conditions.*

9.**Why you should not use inner HTML in JavaScript?**

The answer of this question is - Wait for it -

Inner HTML content is refreshed every time and thus is slower, because of this there is no scope for validation in inner HTML. Therefore, it is easier to insert rogue code in the document and make the web page unstable.

10.**What are some important JavaScript Unit Testing Frameworks?**

There is a pretty long answer of this question-

*Unit.js: It is known as an open-source assertion library running on browser and Node.js. It is extremely compatible with other JavaScript Unit Testing frameworks like Mocha, Karma, Jasmine, QUnit, Protractor, etc. Provides the full documented API of assertion list.*

*QUnit: It is used for both client-side and server-side JavaScript Unit Testing. This Free JavaScript testing framework is used for jQuery projects. It follows Common JS unit testing Specification for unit testing in JavaScript. It supports the Node Long-term Support Schedule.*

*Jasmine: Jasmine is the behavior-driven development framework to unit test JavaScript. It is used for testing both synchronous and asynchronous JavaScript codes. It does not require DOM and comes with an easy syntax that can be written for any test.*

*Karma: Karma is an open-source productive testing environment. Easy workflow control running on the command line. Offers the freedom to write the tests with Jasmine, Mocha, and QU nit. You can run the test on real devices with easy debugging.*

*Mocha: Mocha runs on Node.js and in the browser. Mocha performs asynchronous testing more simply. Provides accuracy and flexibility in reporting. Provides tremendous support of rich features such as test-specific timeouts, JavaScript APIs.*

*Jest: Facebook uses jest so far to test all the JavaScript code. It provides the 'zero-configuration testing experience. Supports independent and non-interrupting running tests without any conflict. Do not require any other setup configuration and libraries.*

*AVA: AVA is a simple JavaScript Unit Testing Framework. Tests are being run in parallel and serially. Parallel tests run without interrupting each other. This testing framework supports asynchronous testing as well. AVA uses sub processes to run the unit test JavaScript.*

##**END**

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