An interview is an important part of the hiring process.
As a JavaScript developer, you must prepare yourself before appearing in an exam or an interview.
Itll increase your chances of getting hired by a reputed company.
So, to help you out, Ive compiled a list of commonly asked JavaScript interview questions.
Each of these questions has a brief answer which you could review below.
So, lets get started.
First of all, what is JavaScript?
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It was initially used on a popular web online window called Netscape Navigator.
But, these days, we can use it for client-side as well as server-side system development.
I dont think someone will ask this, but we shouldnt forget where JavaScript comes from.
Can you list some advantages of JavaScript?
Should we use internal or external JavaScript?
Internal JavaScript is more suitable when we just need to use it on a single web page.
Whereas, always use an external JavaScript file for websites that have multiple web pages.
Why do WordPress plugins like Autoptimize aggregate JavaScript Code in one file?
In turn, it makes a website load faster.
For example, lets say weve included ten JavaScript files on a web page.
What is JavaScript hoisting?
Hoisting is a concept in JavaScript which allows us to use variables and functions even before they are declared.
After that, it starts executing the code.
Learn more about hoisting with my article Understanding Variables, Scope, and Hoisting in JavaScript.
Can you predict the output of the following code?
Code:
Output:
Explanation:
What is JavaScript Strict Mode?
The default behavior of JavaScript is very forgiving in case we make a minor mistake.
It means it will not display any error messages.
Here comes the use of Strict Mode in JavaScript.
What are some alternatives to Svelte?
Svelte is a front-end development framework for the JavaScript programming language.
Some of its popular alternatives include:
What are Self Invoking Functions?
Self Invoking Functions are a little different from normal functions because they are executed immediately where they were declared.
Normally, we first declare a function and later just call it.
But, JavaScript automatically executes the code of Self Invoking Functions at run-time.
A point to be noted is that these functions do not have any name.
In turn, we are unable to recall these types of functions.
They are also known as Anonymous Functions.
Learn more about them in my article Understanding Variables, Scope, and Hoisting in JavaScript.
What is the difference between == and ===?
Both of them are used in JavaScript to perform a comparison between two values.
Is there any difference between null and undefined keywords?
Both of these keywords represent an empty value.
But, there are two basic differences between null and undefined.
Can you tell the difference between function declaration and function expression?
Function Declaration:
Function Expression:
What is a Closure?
A closure in JavaScript is a function inside another function.
Closure Example:
Can you predict the output of these two functions?
And will they return same the output or not?
Output of Function user1()
Output of Function user2()
What is NaN?
In JavaScript, NaN stands for Not a Number.
Its a special value that pops up if were unable to perform an operation.
For example, what if we take a stab at divide a string using a number (e.g.
Hello World / 5).
Can you explain the for-in loop?
The for-in loop is specifically designed to loop through all the objects properties in a step by step manner.
It selects one property from the object in each iteration and performs the required operations on it.
In JavaScript DOM, HTML elements are nested inside one another to form a hierarchy.
It can be determined in two ways which are known as event bubbling and capturing.
In event bubbling, the child element will capture the event first and then propagate it to parent elements.
Whats the difference between JavaScript and ECMA Script?
How do you create a cookie using JavaScript?
In JavaScript, a cookie can be created using a document.cookie object.
Simply assign it a string value that is just a series of key-value pairs separated with semi-colons.
So, if youre not well-prepared then chances are youll end up losing the opportunity.
So, today, I tried to answer some commonly asked JavaScript interview questions.
You may even use it as a reference just before going to an interview.
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