9 JavaScript Interview Questions For 5 Years Of Experience

Updated 9 June 2023

JavaScript is a popular programming language for developing interactive and dynamic web pages. If you are an experienced developer, a strong job interview can help you advance your career. Understanding the types of questions that a recruiter may ask you in a JavaScript interview can help you prepare and secure a role. In this article, we share nine JavaScript interview questions for 5 years of experience with sample answers to help you feel confident in an interview.

Related: 8 Tricky JavaScript Interview Questions With Sample Answers

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9 JavaScript Interview Questions For 5 Years Of Experience With Sample Answers

Here are nine JavaScript interview questions for 5 years of experience, along with sample answers to help you prepare your own:

1. What is your experience with JavaScript and how have you used it in your projects?

An interviewer asks this question to assess your background and proficiency with JavaScript and your ability to apply them in real-world scenarios. Provide specific examples of projects you have worked on where you used JavaScript and highlight the impact your work had on the project.

Example: I have experience working with JavaScript and have used it in several projects. During my last project, I developed a dynamic web page that displayed the data retrieved from a third-party application programming interface (API). I used JavaScript to retrieve and display data from the API on the webpage.

I also incorporated several interactive features, such as drop-down menus and search bars using JavaScript. One of the significant challenges I faced in this project was managing the complexity of the codebase. To overcome this, I implemented a modular approach, breaking the code into smaller manageable components that I could test and debug separately.

Related: How To Become A JavaScript Developer: A Step-By-Step Guide

2. How do you stay current with the latest advancements and updates in the JavaScript ecosystem?

This question aims to understand your commitment to staying updated and informed in this ever-evolving field. Sharing your techniques for remaining aware of industry trends demonstrates your passion for web development and continuous learning. Be specific about the resources you rely on and how you apply the acquired knowledge to your projects.

Example: I follow several online communities and open-source forums to keep myself informed about the latest developments in JavaScript. Additionally, I regularly attend online webinars and conferences to stay updated about the newest trends and advancements. To put what I have learned into practice, I frequently work on personal projects or take part in coding competitions, where I can experiment with new technologies and sharpen my skills. Recently, I experimented with React and Node.js to create a dynamic web application. This enabled me to use my knowledge in a practical setting.

3. How do you handle errors and bugs in your JavaScript code?

Interviewers ask this question to learn about your problem-solving skills and how you troubleshoot errors and bugs in your JavaScript code. When answering this question, provide specific examples of when you encountered faults in your code and the steps you took to resolve them.

Example: I have developed a systematic approach to debugging code when I encounter errors. First, I carefully review the code to identify the source of the problem. Then, I use the browser development tools to identify the part of the code causing the problem. Once I have identified the problem, I use debugging techniques, such as console.log() statements and breakpoints, to isolate and resolve the issue. I also use code linters, such as ESLint, to ensure that my code adheres to best practices and is error-free.

Related: 20 JavaScript Promise Interview Questions (With Answers)

4. What is the difference between let, var and const in JavaScript? When do you use each one?

Here, the hiring manager wants to judge your fundamental knowledge of JavaScript and your understanding of variable declaration. Explain the difference between let, var and const clearly and concisely. Use specific examples to illustrate when and why you use each one.

Example: In JavaScript, let is a block-scoped variable, only accessible within its declared block. Var is function scoped, making it accessible throughout the entire function, even if declared within a block. Const is also block scoped, but it is helpful for constant values that do not require reassigning. I use let for variables with limited scopes, such as loop counters or temporary variables. Var is suitable for variables necessary throughout a function, while const is ideal for defining constant values, such as configuration settings or identifiers.

Related: 27 ES6 Interview Questions (With A Few Example Answers)

5. What is the event loop in JavaScript and how does it work?

Interviewers may ask this question to ascertain your understanding of how JavaScript manages asynchronous code execution and how the event loop works to ensure that the user interface (UI) remains responsive. When answering this question, define the event loop and how it works, and provide an example of how you can use it to handle asynchronous code execution.

Example: The event loop is a mechanism in JavaScript that manages the execution of asynchronous code and ensures that the UI remains responsive. It works by maintaining a queue of messages and a call stack of functions ready for execution. When the call stack is empty, the event loop takes the next message from the queue and executes the corresponding function. For example, when requesting an API, the event loop can continue to run other parts of the program while waiting for the response, rather than halting all execution until it receives a response.

Related: JavaScript Vs Java: What Are The Fundamental Differences?

6. What is a closure in JavaScript? Share an example of how you can use closure in your code

This question helps show your understanding of closures in JavaScript and your ability to apply them to solve programming problems. Start by defining what a closure is and how it works, and include its relationship with lexical scope in your answer.

Example: A closure is a function that has access to variables in its outer function's scope, even after the outer function has returned. Closures can encapsulate functionality and protect variables from the global scope. One example of a closure is a counter function, which produces a new value each time it returns.

To achieve this, the outer function creates a variable to track the current count and returns an inner function that increments the count and returns its current value. As the count variable definition is in the outer function, it is not accessible from outside the closure. This makes it a private variable only accessible by the inner function, which closure returns.

Related: Frontend vs. Backend Development: What Is the Difference?

7. What is the difference between synchronous and asynchronous code in JavaScript?

This question aims to assess your understanding of different code execution patterns. When answering, briefly explain the main differences between synchronous and asynchronous code, and mention some common techniques for handling asynchronous code in JavaScript.

Example: Synchronous code in JavaScript means that each operation happens one after the other, causing the program to wait to complete a task before moving on to the next one. Asynchronous code allows the execution of multiple tasks concurrently without waiting for a previous task to finish. This helps improve the overall performance and user experience of a web application. Some common techniques for handling asynchronous code in JavaScript are callbacks, promises and async/await.

Related: What Is Asynchronous Programming And When To Use It?

8. What is the difference between the apply() and call() methods in JavaScript?

The interviewer asks this question to test your understanding of particular JavaScript functions. They want to discover your ability to use the apply() and call() methods to run them with a specific context and pass dynamic arguments. Use specific details to illustrate when and why you can use each approach.

Example: Apply() and call() are both methods in JavaScript that can invoke functions with specific values and arguments. The difference between the two is how they pass arguments to the function. Call() passes arguments one by one, while apply() passes an array of arguments. In previous projects, I used call() when it was necessary to pass a few arguments to a function and apply() while passing a variable number of arguments or when the arguments are in an array.

Related: 13 Advanced JavaScript Interview Questions With Answers

9. What is the spread operator? How is it different from the rest parameter in JavaScript?

The spread operator and rest parameter are JavaScript features that help manage arrays and objects more effectively. Here, the interviewer aims to assess your ability to apply these concepts in real-world scenarios. Focus on distinguishing between the two clearly and demonstrate your ability to use them when writing code.

Example: Three dots denote the spread operator. It helps to unpack elements from arrays or objects. For example, you can use it to merge two arrays, such as const mergedArray = [...array1, ...array2]. Though you use three dots to represent the rest parameter, it gathers multiple function arguments into a single array. You can create a function using rest, which accepts multiple arguments and stores them in an array. One such function is sum(...numbers) { / ... / }.

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