Crack the Code: Expert Tips for JavaScript Interviews

Feeling the nerves before your big interview?

You're not alone, but fear not—preparation is your secret weapon.

Imagine walking in as confident as Hermione Granger before an exam. That's the level of readiness we're aiming for. 😉

Why focus on JavaScript?

Well, in top tech companies like Amazon, Netflix, Google, and Instagram, JavaScript is the star of the show.

It's the language that powers web browsers!

Making it a fundamental skill for anyone aspiring to excel in interviews to land their dream job.

Tech companies are on the hunt for engineers who can code flawlessly in JavaScript. 

Recruiters want problem-solvers who can navigate software development challenges with finesse.

Whether it's crafting interactive web pages or integrating apps seamlessly. JavaScript is the key to unlocking these opportunities!

In this blog, I'll guide you through the core JavaScript concepts  and share valuable tips to help you stand out in your interview. 

Are you ready to delve into the world of JavaScript? Let's this blog equip you with the skills you need to crack the code and succeed in your interview! ✨

Work 1:1 with an SDE 3 – get personalised help with Javascript Interviews.

What is JavaScript?

JavaScript, born from Brendan Eich's hands in 1995, has evolved into one of the most prevalent web development languages.

Initially crafted for dynamic web pages, JavaScript scripts seamlessly integrate with HTML. Thus, executing automatically upon page load.

What began as a tool for web interactivity has transcended boundaries!

Today, JavaScript has grown into a powerhouse. Standing tall as one of the top web development languages. 

Javascript is an object-oriented programming language. It has metamorphosed into Node.js. Enabling the creation of real-time applications, online streaming platforms, and video games. 

The emergence of JavaScript frameworks, encompassing built-in libraries, has streamlined development processes. 

These frameworks empower developers to focus on creative aspects by automating repetitive tasks, ushering in an era of efficient and dynamic application development.

JavaScript Basics: Variables in JavaScript

In JavaScript, variables are used to store values and are essential in programming. 

Unlike some other languages, JavaScript is loosely-typed, meaning you don't have to specify the type of variable when declaring it. 

There are three ways to declare variables in JavaScript: var, let, and const.

Note: In JavaScript, putting a semi-colon after the end of a statement is optional.

Fundamental JavaScript Concepts

1. JS Execution

JavaScript code is executed line by line. 

When you visit a website, the browser's JavaScript engine interprets and runs the JavaScript code on that page. 

It processes instructions, enabling dynamic content, animations, and interactive features.

2. Data Types

JavaScript has several data types, including:

➡️Strings (text), 

➡️Numbers (integers or decimals), 

➡️Booleans (true/false values), 

➡️Arrays (lists of data), and 

➡️Objects (collections of key-value pairs)

Understanding data types helps in managing and manipulating different kinds of information.

3. Hoisting

Hoisting is a JavaScript behaviour where variable and function declarations are moved to the top of their scope during the compilation phase.

This allows you to use variables and functions before they are declared in your code.

4. Scoping

Scoping defines where variables can be accessed. 

Variables declared with var are function-scoped. While those declared with let and const are block-scoped. 

Block scope means the variable is only accessible within the nearest pair of curly braces {}.

5. Functions

Functions in JavaScript are blocks of code that can be defined and reused. 

They can take inputs (parameters), perform actions, and return values. Functions are essential for organising code into manageable and reusable pieces.

6. Function Currying

Function currying involves creating a series of specialised functions from a general function. 

It allows you to partially apply arguments to a function, creating new functions tailored for specific use cases. 

This technique aids in code modularity and reusability.

6. Closures

Closures are functions within functions that remember the scope in which they were created. 

They capture and "remember" the variables from their outer function even after the outer function has finished executing. 

Closures are powerful for maintaining state and creating private variables in JavaScript.

7. "This" Keyword

This keyword in JavaScript refers to the object to which a function belongs when it is called. 

It allows functions to work with different objects based on how they are invoked. Thus, enabling flexible and dynamic code behaviour.

8. Prototypal Inheritance

JavaScript objects can inherit properties and methods from other objects through their prototypes. 

Prototypal inheritance allows objects to inherit features from other objects, promoting code reuse and organisation.

9. Callbacks and Async JS

Callbacks are functions passed as arguments to other functions and executed later. Often used in asynchronous operations. 

Async JavaScript, including Promises and Async/await, simplifies asynchronous programming.  

This ensures smooth handling of tasks like fetching data from servers without freezing the user interface. 

10. Event Loop

The event loop is a fundamental mechanism in JavaScript. As it ensures non-blocking asynchronous operations. 

It manages the execution of tasks, allowing JavaScript to handle multiple operations simultaneously. Such as user interactions and data fetching, without causing delays or freezing the application.

Learn Javascript Concepts in detail from a pro. Connect with me for long-term mentorship and let’s bag your dream tech job together!

Real-World Examples for Closures

Remember: Closures are like magical memory boxes for functions. 

Example: Event handling. 

Imagine you have a button on a webpage, and you want to perform different actions when the button is clicked, depending on the context. Closures help you achieve this. 

function setupEventHandlers() {

    const button = document.getElementById('myButton');

    // Closure that remembers 'button'

    button.addEventListener('click', () => {

        console.log('Button clicked!');

        // Here, we still have access to the 'button' variable

    });

}

‍

setupEventHandlers();

‍

Here's how it works:

1. Creating a Function:

We define `setupEventHandlers`, which sets up an event listener for a button with the id 'myButton.' Inside it, the `button` constant is defined.

2. Creating a Closure:

The event listener function is a closure. It remembers the `button` variable, even after `setupEventHandlers` has been executed. 

So, when the button is clicked, it can still access and use the `button` variable.

Closures make JavaScript code more powerful and flexible.

Real-World Examples for Function Currying

Remember: Function currying is akin to preparing a recipe step by step. 

Example: Calculating prices with different tax rates based on regions. Function currying can simplify this task.

// A general function for calculating prices

function calculatePrice(basePrice, taxRate) {

    return basePrice * (1 + taxRate);

}

// Curried functions for different regions

function calculatePriceInRegion(region) {

    if (region === 'USA') {

        return (basePrice) => calculatePrice(basePrice, 0.08); // 8% tax in the USA

    }

    if (region === 'EU') {

        return (basePrice) => calculatePrice(basePrice, 0.20); // 20% tax in the EU

    }

}

‍

// Usage

const calculateInUSA = calculatePriceInRegion('USA');

console.log(calculateInUSA(100)); // Output: 108

‍

const calculateInEU = calculatePriceInRegion('EU');

console.log(calculateInEU(100)); // Output: 120

‍

Function currying enhances code readability and maintainability, especially for complex functions with multiple parameters.

Navigating the JavaScript Interview Application Process

1. Research

Research tech companies or startups that align your skills with their technology stack.

Understand the various JavaScript-related roles such as Frontend Developer, Full Stack Developer, or JavaScript Engineer.

2. Portfolio and GitHub

Showcase your JavaScript projects in a portfolio. Highlight your role, technologies used, and the problems you solved.

Ensure your GitHub profile is updated with your recent JavaScript projects. Include well-documented code and README files.

3. Application Submission

Prepare a tailored resume emphasising your skills, projects, and experience. Highlight any certifications or online courses that verify your skills.

Write a cover letter explaining your passion for the subject. Mention specific projects or technologies you've worked on.

4. Networking

Forge connections with professionals and actively take part in technical discussions.

Engage in coding forums such as StackOverflow to broaden your network and knowledge.

Suggested Reading: Unlocking Career Success: The Power of Your Mentor's Network

5. JavaScript Interview Preparation

Review fundamental JavaScript concepts like closures, promises, and asynchronous programming.

Brush up on popular JavaScript frameworks and libraries. Be ready to discuss projects where you've utilised these technologies.

Practice solving JavaScript coding problems on platforms like LeetCode or HackerRank. 

Be prepared for technical assessments that test your JavaScript skills. Practice coding challenges regularly.

Some interviews might involve pair programming exercises. Practice collaborating on coding problems with a partner.

Commonly asked Javascript interview questions

1. Write a function to reverse a string.
2. Write a function to find the largest number in an array.
3. Write a function to remove duplicates from an array.
4. Write a function to implement a linked list.
5. Write a function to implement a binary search tree.
6. Explain how to use promises to handle asynchronous code.
7. Explain how to use callbacks to implement event handling.
8. Explain how to use classes to create reusable code.
9. Explain how to use DOM manipulation to modify the HTML DOM.
10. Explain how to use regular expressions to validate user input.

Looking for More Help?

If you find these questions challenging, don't worry! 

JavaScript can be tricky, especially when you're just starting out. Don't hesitate to reach out for personalised guidance. 

We can schedule one-on-one mentorship sessions where we can go over these javascript interview questions in detail.

Together, we can work through the challenges. Then, move forward by strengthening your understanding of javascript concepts. 

Feel free to connect with me, and let's conquer these challenges together!

Helpful guides:

Why is Mentorship Better Than Online Pre-recorded Courses?

How to Choose the Right Mentor at Preplaced?