Introduction
You sit in a developer interview. After a few basic questions, the interviewer often shifts to JavaScript. It happens in many frontend and full stack roles. They want to see how you think when working with the language.
Some questions stay simple. Others test deeper ideas like scope, callbacks, promises, or closures. That is why many candidates review JavaScript Interview Questions and Answers before an interview. It helps bring back concepts that may not appear in daily work.
Reading JavaScript Interview Questions and Answers also shows how interviewers frame problems. When you see those patterns early, it becomes easier to respond during the actual discussion. The goal is not to memorize answers. The goal is to understand how JavaScript behaves when code runs.
List of JavaScript Interview Questions for Freshers
- 1. What is JavaScript?
- 2. What features does JavaScript have?
- 3. What does JavaScript’s “this” keyword mean?
- 4. What are the scopes of a variable?
- 5. What are the JavaScript naming conventions for variables?
- 6. How is JavaScript code debugged?
- 7. What does JavaScript callback mean?
- 8. Tell me how you will add JavaScript code to an HTML file.
- 9. Explain cookies.
- 10. Differentiate between Var and Let.
- 11. How to create a cookie using JavaScript?
- 12. What JavaScript arrow functions are there?
- 13. Why is the isNaN function used?
- 14. Which is quicker between ASP and JavaScript?
- 15. Explain negative infinity
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JavaScript Technical Interview Questions and Answers for Freshers
1. What is JavaScript?
JavaScript is a well-liked web scripting language that is useful for both client-side and server-side programming. Web browsers that parse and run HTML pages can have JavaScript added to them. JavaScript is compatible with object-oriented programming.
2. What features does JavaScript have?
JavaScript has the following features:
- Programming language that is lightweight and interpretable, suitable for multiple systems
- Object-oriented code source
- combining a variety of back-end and front-end technologies
- specifically utilized in the creation of network-based applications
3. What does JavaScript’s “this” keyword mean?
The JavaScript keyword “this” identifies the object now being called. Constructors typically use it to set the values for object properties.
4. What are the scopes of a variable?
In a JavaScript application, a variable’s scope refers to the location of its declarations and definitions. A variable can have one of two scopes:
Global Scope: Variables with global scope can be accessed from anywhere in JavaScript code.
Local Scope: Only the function that has a local variable can access it.
5. What are the JavaScript naming conventions for variables?
The following are the guidelines for naming variables in JavaScript.
- Variable and reserved keywords cannot share the same name. Examples include var, let, and const.
- Variable names cannot start with a number. At first, they can only contain letters or underscores.
- It matters when it comes to variable names.
6. How is JavaScript code debugged?
Any modern web browser, such as Chrome, Firefox, and others, includes an integrated debugger that can be accessed at any time by pressing the appropriate key, which is usually F12. Debugging tools enable users to perform a wide range of operations.
Furthermore, we can debug JavaScript code straight from within a code editor used to create JavaScript apps, such as Visual Studio Code, Atom, Sublime Text, or another one.
7. What does JavaScript callback mean?
JavaScript functions can accept input from other functions and return objects from other functions since they are objects.
Callbacks are JavaScript functions that are provided as arguments or parameters to other functions. This function will be called whenever the provided function is run.
Check out: JavaScript Course Syllabus PDF
8. Tell me how you will add JavaScript code to an HTML file.
There are two major ways to embed JavaScript code:
- When only a few lines of scripting are required on a web page, we can write JavaScript code within the script element of the same HTML document.
- When a JavaScript source file is imported into an HTML document, the entire web page can be created without clogging the code.
9. Explain cookies.
A cookie is often a short data file transmitted and saved on the user’s computer by the web browser used to access the website. Cookies are used to store data for later use and to monitor user behavior on websites.
10. Differentiate between Var and Let.
In JavaScript, utilize the let and var statements to specify variables and methods. A block scopes the let keyword, while a function scopes the var keyword. Aside from that, not much distinguishes the two.
11. How to create a cookie using JavaScript?
The most simple approach for creating JavaScript cookies is as follows:
document.cookie = “key1 = value1; key2 = value2; expires = date”;
12. What JavaScript arrow functions are there?
Arrow functions allow you to write JavaScript functions quickly and simply.
Syntax:
const helloWorld = () => {
console.log(“hello world!”);
};
List of JavaScript Interview Questions for Experienced
- 16. Can JavaScript code be divided into multiple lines?
- 17. Describe JavaScript’s Higher Order Functions.
- 18. What is a self-invoking function in JavaScript?
- 19. What distinguishes JavaScript’s exec() and test() methods from one another?
- 20. What benefits does utilizing External JavaScript offer?
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JavaScript Technical Interview Questions and Answers for Experienced
16. Can JavaScript code be divided into multiple lines?
It is possible to split the JavaScript code into many lines within a string statement. To break it, use the backslash ‘\’.
Example:
document.write(“A Lifetime Career Guidance\ by SLA”)
The code-breaking line is avoided by JavaScript, which is not optimal.
let gfg= 10, GFG = 5,
SLA =
gfg + GFG;
17. Describe JavaScript’s Higher Order Functions.
Higher-order functions are those that perform operations on other functions, either by returning them or by accepting them as arguments.
Because functions in JavaScript are first-class citizens, they lead to higher-order functions.
Example:
function higherOrder(fn) {
fn();
}
higherOrder(function() { console.log(“Hello world”) });
function higherOrder2() {
return function() {
return “Do something”;
}
}
var x = higherOrder2();
x() // Returns “Do something”
18. What is a self-invoking function in JavaScript?
A self-invoking expression is automatically invoked (initiated) without any request. A function expression will run automatically if it has an a() after it. It is not possible to call a function definition by itself.
An anonymous function can be used to run a function automatically when it is described; otherwise, it will not be called again. Normally, we define functions and call them. Furthermore, these kinds of functions have no name.
19. What distinguishes JavaScript’s exec() and test() methods from one another?
- JavaScript uses the RegExp expression functions test() and exec().
- To search a string for a specific pattern, we’ll use exec (). If the pattern is found, the function will return it straight; if not, it will return ’empty’.
- To locate a string for a given pattern, we’ll utilize test(). When it locates the provided text, it will return the Boolean value “true”; otherwise, it will return “false.”
20. What benefits does utilizing External JavaScript offer?
External JavaScript refers to JavaScript code (script) that is written in a different file ending in.js. It is linked inside the element of the HTML page that contains the code.
A few benefits of using external JavaScript are
- It allows designers and web developers to collaborate on HTML and JavaScript files.
- The code can be used again.
- The readability of code in external Javascript is straightforward.
Check out: JavaScript Training in OMR
Conclusion
JavaScript shows up in many developer interviews. A recruiter may ask about functions, scope, events, or asynchronous code. Sometimes the question starts simple. Then it slowly moves into deeper concepts.
Because of that, many candidates read JavaScript Interview Questions and Answers before attending interviews. It helps them recall ideas they learned earlier. A short revision can make a big difference when you try to explain code during a discussion.
Still, the best learning happens when you write code yourself. Try small programs. Test different functions. Break things and fix them again. That habit improves your confidence over time.
If you want to learn JavaScript step by step with guided practice, check our JavaScript Training in Chennai. The course focuses on coding exercises and real web development tasks.
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