Top 10 Expert-Crafted JavaScript Coding Interview Questions

Are you gearing up for your next frontend interview? Whether you're just starting your journey or sharpening your skills, mastering JavaScript is a must. In interviews, JavaScript questions often dive into core concepts and practical scenarios, testing your understanding and problem-solving abilities.

This guide is here to help! We’ve compiled 10 crucial JavaScript questions that every budding frontend developer should know. With clear explanations and practical examples, you’ll be better prepared to handle these topics and impress your interviewers.

Let’s jump in and boost your confidence for your next big opportunity!

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1. Debouncing: Controlling Event Frequency in JavaScript

Debouncing is a performance optimization technique that ensures a function is executed only after a specified delay following the last event. It’s particularly useful for handling rapid, repetitive events such as user input, scrolling, or window resizing, preventing unnecessary function calls and improving efficiency.

Example: Using Debounce with Lodash

Here’s how to use Lodash’s debounce function to manage frequent user input:

import { debounce } from 'lodash';

const searchInput = document.getElementById('search-input');

const debouncedSearch = debounce(() => {
  // Perform the search operation here
  console.log('Searching for:', searchInput.value);
}, 300);

searchInput.addEventListener('input', debouncedSearch);

In this example, the search operation will only execute if the user pauses typing for 300 milliseconds, reducing the number of search requests and improving performance.

Key Features of Debouncing

• Event Delay: Executes the function only after the specified time has elapsed since the last event.
• Performance Optimization: Prevents redundant operations, such as frequent API calls or heavy calculations, during rapid input events.
• Flexible Timing Options:
  • Leading: Executes the function at the start of the delay period.
  • Trailing: Executes the function at the end of the delay period.
  • Max Wait: Ensures the function is executed after a maximum delay, even with continuous input.

Why It Matters in Interviews

• Real-World Applications: Demonstrates knowledge of practical techniques for improving application performance.
• Problem-Solving Skills: Tests understanding of event handling and function execution management.
• Advanced Concepts: Candidates may be asked to compare debouncing with throttling or implement a custom debounce function from scratch.

Bonus Insights

• Browser Events: Debouncing is highly effective for optimizing scroll, resize, and input events, which can trigger rapidly and affect performance.
• Lodash Alternatives: While Lodash is a popular choice, you can create custom debounce implementations tailored to specific needs.
• Hybrid Strategies: Combine debouncing with throttling in complex scenarios for optimal performance.

Take It a Step Further

• Write a Custom Debounce Function: Implement your own version of debounce to gain a deeper understanding.
• Experiment with Timing Variants: Practice using leading and trailing edge callbacks to suit different use cases.
• Apply in Real Projects: Integrate debounce logic into a search bar, infinite scroll, or form validation to see its impact.

Practice implementing a Debounce function on GreatFrontEnd

2. Understanding Promise.all in JavaScript

Promise.all() is a powerful method in JavaScript for managing multiple asynchronous operations simultaneously. It takes an array of promises and returns a single promise that resolves when all the promises in the array resolve or rejects if any one of them fails. This makes it ideal for handling dependent or concurrent tasks efficiently.

Example: Fetching Multiple URLs

Here’s how Promise.all() works in practice:

const promise1 = fetch('https://api.example.com/data/1');
const promise2 = fetch('https://api.example.com/data/2');
const promise3 = fetch('https://api.example.com/data/3');

Promise.all([promise1, promise2, promise3])
  .then((responses) => {
    // Executes only when all promises are resolved.
    console.log('All responses:', responses);
  })
  .catch((error) => {
    // Handles errors from any of the promises.
    console.error('Error:', error);
  });

In this example, data is fetched from three URLs simultaneously. The .then() block runs only when all promises resolve, and the .catch() block handles any rejection.

Why It Matters in Interviews

• Asynchronous Mastery: Demonstrates understanding of asynchronous workflows, an essential skill in modern web development.
• Error Handling: Tests your ability to manage success and failure scenarios effectively.
• Real-World Application: Many front-end tasks, like fetching multiple APIs or running parallel computations, rely on Promise.all.

Bonus Insights

• Performance: Using Promise.all can significantly improve performance by running promises concurrently rather than sequentially.
• Related Methods:
  • Promise.race(): Resolves or rejects as soon as the first promise in the array settles.
  • Promise.any(): Resolves as soon as any promise resolves, ignoring rejections unless all promises fail.
• Polyfill Practice: Writing a polyfill for Promise.all is a great way to deepen your understanding of promise mechanics.

Take It a Step Further

• Compare with Sequential Execution: Analyze performance differences between Promise.all() and sequential promise execution.
• Explore Advanced Patterns: Combine Promise.all() with other promise methods like Promise.race() or Promise.allSettled() for complex workflows.
• Error Isolation: Implement custom logic to handle individual promise rejections without failing the entire batch.

Practice implementing Promise.all() on GreatFrontEnd

3. Understanding Deep Equality in JavaScript

Deep equality is a key concept in JavaScript for comparing objects or arrays to see if they are structurally identical. Unlike shallow equality, which only checks if references are the same, deep equality verifies that all values, including those in nested structures, are equal.

Example: Implementing a Deep Equal Function

Here’s a simple implementation of a deep equality check:

function deepEqual(obj1, obj2) {
  if (obj1 === obj2) return true;

  if (
    obj1 == null ||
    typeof obj1 !== 'object' ||
    obj2 == null ||
    typeof obj2 !== 'object'
  )
    return false;

  let keys1 = Object.keys(obj1);
  let keys2 = Object.keys(obj2);

  if (keys1.length !== keys2.length) return false;

  for (let key of keys1) {
    if (!keys2.includes(key) || !deepEqual(obj1[key], obj2[key])) return false;
  }

  return true;
}

// Example usage
const object1 = {
  name: 'John',
  age: 30,
  address: {
    city: 'New York',
    zip: '10001',
  },
};

const object2 = {
  name: 'John',
  age: 30,
  address: {
    city: 'New York',
    zip: '10001',
  },
};

console.log(deepEqual(object1, object2)); // true

In this example, the deepEqual function recursively compares two objects or arrays. It checks:

1. If they reference the same memory location.
2. If they are both non-null objects.
3. If their keys and values match, including nested structures.

Why It Matters in Interviews

• Practical Applications: Many real-world tasks, such as comparing state objects in frameworks like React, require deep equality checks.
• Core Concepts: Tests knowledge of recursion, object traversal, and handling edge cases in JavaScript.
• Distinguishing Deep vs. Shallow Comparisons: Demonstrates understanding of the differences between equality by reference and equality by value.

Bonus Insights

• Performance: Deep equality checks can be computationally expensive for large, deeply nested objects. Optimization techniques may be needed in performance-critical applications.
• Libraries: Tools like Lodash and Ramda provide built-in deep equality functions, but implementing your own is an excellent learning experience.
• Edge Cases: Understanding how to handle special cases like circular references is critical for robust implementations.

Take It a Step Further

• Handle Circular References: Modify the function to support circular references using a cache or WeakMap.
• Test Performance: Benchmark the function with large datasets and compare it to library implementations.
• Integrate into Real-World Projects: Use deep equality checks in scenarios like data comparison, unit tests, or state management.

Practice implementing Deep Equal on GreatFrontEnd

4. Understanding the EventEmitter in JavaScript

The EventEmitter class is a versatile tool in JavaScript for managing event-driven programming. It enables objects to define, listen to, and trigger custom events based on specific actions or conditions. This aligns with the observer pattern, where the event emitter maintains a list of subscribers (observers) and notifies them whenever an event occurs. This concept is a cornerstone in frameworks and libraries that deal with dynamic, interactive features. It’s also a key component of the Node.js API.

Here's an example to see the EventEmitter in action:

// Example usage
const eventEmitter = new EventEmitter();

// Subscribe to an event
eventEmitter.on('customEvent', (data) => {
  console.log('Event emitted with data:', data);
});

// Emit the event
eventEmitter.emit('customEvent', { message: 'Hello, world!' });

In this example, an event named customEvent is defined. Listeners subscribed to this event are notified whenever the event is emitted. This allows for dynamic communication between different parts of an application.

Why It Matters in Interviews

The EventEmitter is a popular topic in front-end interviews for a variety of reasons:

• Key Concepts: It tests understanding of object-oriented programming, closures, and the this keyword.
• Practical Scenarios: Questions might involve creating an EventEmitter from scratch or implementing additional functionality like one-time listeners or removing event subscriptions.
• Debugging Skills: Knowledge of memory leaks and how unhandled listeners can cause performance issues is often explored.

Bonus Insights

• Real-World Examples: The observer pattern implemented by EventEmitter is widely used in libraries like RxJS, Redux, and even React when handling component lifecycles or state changes.
• Asynchronous Event Handling: EventEmitter can handle asynchronous operations, making it suitable for real-time systems like chat applications or notifications.
• Practical Features: Learn about the once method for events that should fire only once, reducing unnecessary listener management.

Take It a Step Further

• Build Your Own: Try implementing a simplified version of the EventEmitter class to reinforce your understanding.
• Explore Node.js: Dive deeper into how EventEmitter is used in Node.js for managing streams, HTTP requests, and other asynchronous processes.
• Debugging Mastery: Learn techniques to identify and handle unintentional memory leaks caused by unresolved event listeners.

Practice building an Event Emitter on GreatFrontEnd

5. Exploring Array.prototype.reduce() in JavaScript

The Array.prototype.reduce() method is one of the most powerful tools in JavaScript for processing arrays. It works by applying a callback function to an accumulator and each element of the array (in sequence) to transform the array into a single output value. This method is incredibly versatile, lending itself to tasks like summing numbers, flattening nested arrays, or even building complex data structures.

Here’s an example of using reduce() to calculate the sum of an array:

// Example: Summing numbers in an array
const numbers = [1, 2, 3, 4, 5];
const sum = numbers.reduce(function (accumulator, currentValue) {
  return accumulator + currentValue;
}, 0);

console.log(sum); // Output: 15

In this example, reduce() iterates through the numbers array, adding each number to the accumulator, which starts at 0. Once all elements have been processed, it returns the final result, 15.

Why It Matters in Interviews

The reduce() method is a staple of functional programming in JavaScript and frequently comes up in front-end interviews. It tests a candidate's ability to:

• Work with functional-style APIs.
• Understand array iteration and transformation techniques.
• Manage accumulator state effectively across iterations.

Companies often include questions about reduce() alongside methods, such as map(), filter, and concat(). Mastering reduce() demonstrates a deep understanding of JavaScript array methods, prototypes, and even polyfill implementation.

Bonus Insights

• Callback Parameters: The reduce() callback function accepts four parameters: accumulator, currentValue, currentIndex, and the array itself. Understanding all these parameters can help in solving more complex problems.
• Handling Sparse Arrays: Unlike some array methods, reduce() skips uninitialized elements in sparse arrays, which can affect the result in unexpected ways.
• Array Mutation: Be cautious about mutating the array being reduced, as it can lead to unpredictable behavior.
• Practical Uses: Beyond summing numbers, reduce() is often used for tasks like:
  • Flattening nested arrays.
  • Grouping data into categories.
  • Creating a frequency map of elements.

Take It a Step Further

• Write a Polyfill: Try implementing a custom polyfill for reduce() to better understand its internal mechanics.
• Advanced Usage: Practice using reduce() for multi-step transformations, like combining mapping and filtering into a single operation.
• Explore Alternatives: Understand when to use reduce() versus other array methods like map() or filter() for more readable and maintainable code.

Practice building the Array.prototype.reduce() function on GreatFrontEnd

6. Flattening Arrays in JavaScript

In JavaScript, "flattening" refers to the process of converting a nested array into a single-level array. This technique is incredibly useful for simplifying complex data structures, making them easier to process and manipulate. With the introduction of the Array.prototype.flat() method in ES2019, flattening arrays has become a breeze for modern developers.

Here’s how flat() works:

// Example: Flattening a nested array
const nestedArray = [1, [2, [3, [4, [5]]]]];
const flatArray = nestedArray.flat(Infinity);

console.log(flatArray); // Output: [1, 2, 3, 4, 5]

In this example, the flat() method is applied with a depth of Infinity to completely flatten a deeply nested array. The flat() method also allows specifying a depth argument to control how many levels of nesting should be flattened, making it versatile for various use cases.

Before ES2019, developers relied on custom implementations or libraries like Lodash to achieve array flattening. Below is an example of a custom flattening function using recursion:

// Custom implementation of flattening an array
function flattenArray(arr) {
  return arr.reduce((acc, val) => {
    return Array.isArray(val) ? acc.concat(flattenArray(val)) : acc.concat(val);
  }, []);
}

const nestedArray = [1, [2, [3, [4, [5]]]]];
const flatArray = flattenArray(nestedArray);

console.log(flatArray); // Output: [1, 2, 3, 4, 5]

The flattenArray function recursively processes each element in the array, using the reduce() method to concatenate values into a single-level array. This demonstrates a deeper understanding of recursion and array manipulation.

Why It Matters in Interviews

• Key Skill: Flattening arrays highlights a developer's ability to manage and simplify nested data structures, a common task in real-world applications.
• Custom Implementation: Interviewers often ask candidates to write their own flattening functions to test their understanding of recursion, higher-order array methods like reduce(), and problem-solving abilities.
• Modern vs. Legacy: Knowing both the flat() method and older approaches demonstrates versatility and adaptability to different coding environments.

Bonus Insights

• Performance Considerations: The flat() method is optimized for modern JavaScript engines, but custom implementations may be more flexible or performant in specific scenarios.
• Practical Use Cases: Flattening is frequently required when dealing with deeply nested JSON data, hierarchical datasets, or transforming API responses into a usable format.
• Alternative Tools: Libraries like Lodash provide additional utility methods for flattening arrays with fine-grained control and performance enhancements.

Take It a Step Further

• Implement a Polyfill: Create a polyfill for Array.prototype.flat() to gain a deeper understanding of how it works.
• Optimize for Depth: Modify the custom implementation to handle specific depths for flattening instead of always going infinite.
• Explore Real-World Examples: Practice flattening arrays derived from complex API responses or nested datasets to simulate real-world scenarios.

Practice implementing Flatten function on GreatFrontEnd

7. Merging Data in JavaScript

Data merging is a fundamental concept in JavaScript, involving the combination of multiple objects or arrays into a unified structure. It’s especially useful when handling complex datasets or integrating data from various sources. JavaScript offers several methods to accomplish this, from the versatile spread operator to utility libraries like Lodash.

Merging Objects

Using the Spread Operator

The spread operator (...) provides a concise and modern approach to merge objects. It creates a new object by copying properties from source objects, with later properties overwriting earlier ones if there are conflicts.

const obj1 = { a: 1, b: 2 };
const obj2 = { b: 3, c: 4 };

const mergedObj = { ...obj1, ...obj2 };

console.log(mergedObj); // Output: { a: 1, b: 3, c: 4 }

In this example, obj2’s b property overwrites obj1’s b property in the resulting object.

Using Object.assign()

Object.assign() is another method to merge objects by copying all enumerable properties from source objects to a target object.

const obj1 = { a: 1, b: 2 };
const obj2 = { b: 3, c: 4 };

const mergedObj = Object.assign({}, obj1, obj2);

console.log(mergedObj); // Output: { a: 1, b: 3, c: 4 }

Merging Arrays

Using the Spread Operator

The spread operator can also merge arrays by concatenating them.

const array1 = [1, 2, 3];
const array2 = [4, 5, 6];

const mergedArray = [...array1, ...array2];

console.log(mergedArray); // Output: [1, 2, 3, 4, 5, 6]

Using Array.concat()

The concat() method merges two or more arrays into a new array.

const array1 = [1, 2, 3];
const array2 = [4, 5, 6];

const mergedArray = array1.concat(array2);

console.log(mergedArray); // Output: [1, 2, 3, 4, 5, 6]

Deep Merging

For merging deeply nested objects or arrays, a custom function or utility library like Lodash is typically used. Here’s an example of a simple recursive deep merge function:

function deepMerge(target, source) {
  for (const key in source) {
    if (source[key] instanceof Object && key in target) {
      Object.assign(source[key], deepMerge(target[key], source[key]));
    }
  }
  Object.assign(target || {}, source);
  return target;
}

const obj1 = { a: 1, b: { x: 10, y: 20 } };
const obj2 = { b: { y: 30, z: 40 }, c: 3 };

const mergedObj = deepMerge(obj1, obj2);

console.log(mergedObj); // Output: { a: 1, b: { x: 10, y: 30, z: 40 }, c: 3 }

Using Lodash merge

The _.merge function from Lodash is a powerful utility for deep merging. It recursively merges nested properties from source objects into a target object.

const _ = require('lodash');

const obj1 = { a: 1, b: { x: 10, y: 20 } };
const obj2 = { b: { y: 30, z: 40 }, c: 3 };

const mergedObj = _.merge({}, obj1, obj2);

console.log(mergedObj); // Output: { a: 1, b: { x: 10, y: 30, z: 40 }, c: 3 }

In this example, Lodash's _.merge ensures that nested properties are merged correctly and efficiently.

Why It Matters in Interviews

• Practical Skills: Data merging demonstrates your ability to manipulate and organize complex data structures, a critical task in many front-end applications.
• Key Topics: Candidates may be asked to implement object or array merging from scratch to test their understanding of recursion, spread operators, or higher-order functions.
• Real-World Relevance: Knowledge of merging techniques is invaluable when dealing with nested APIs, state management in frameworks like React, or combining configuration objects.

Bonus Insights

• Conflict Resolution: Understand how conflicts are resolved, such as how duplicate keys in objects or arrays are handled during merging.
• Performance: Consider performance implications, especially when merging large datasets or deeply nested structures.
• Immutable Patterns: Explore ways to merge data immutably, which is a common practice in modern front-end development.

Take It a Step Further

• Custom Implementations: Write your own deep merge function with added features like key prioritization or merging arrays differently.
• Learn Lodash: Dive deeper into Lodash's merge and other related functions to expand your toolkit.
• Real-World Scenarios: Practice merging deeply nested data structures from APIs or configuration files to simulate real-world use cases.

Practice building Data Merging function on GreatFrontEnd

8. getElementsByClassName: Selecting Elements by Class in JavaScript

The getElementsByClassName method is a simple and efficient way to select DOM elements using their class names. It returns a live HTMLCollection, meaning it updates automatically when the DOM changes.

Basic Usage

To use getElementsByClassName, call it on the document object and provide the class name(s) as an argument:

// Select all elements with the class name "example"
const elements = document.getElementsByClassName('example');

// Loop through the selected elements
for (let i = 0; i < elements.length; i++) {
  console.log(elements[i].textContent);
}

Selecting Multiple Class Names

You can pass multiple class names separated by spaces to select elements that match all specified classes:

const elements = document.getElementsByClassName('class1 class2');

The Live Nature of HTMLCollection

The HTMLCollection returned by getElementsByClassName is live, so it reflects any additions or removals of elements with the specified class in real time.

Alternative: querySelectorAll

For more advanced selection needs, use querySelectorAll, which supports complex CSS selectors. Unlike getElementsByClassName, it returns a static NodeList:

const elements = document.querySelectorAll('.example');

Why It Matters in Interviews

• Core Knowledge: It tests your understanding of DOM traversal and manipulation.
• Efficiency: Knowing when to use getElementsByClassName can improve performance, especially in scenarios involving bulk selections.
• Dynamic Updates: Understanding the live behavior of HTMLCollection vs. the static nature of NodeList demonstrates deeper DOM expertise.

Bonus Insights

• Performance: getElementsByClassName is faster than querySelectorAll for simple class-based selections.
• Flexibility: While querySelectorAll is more versatile, getElementsByClassName is ideal for straightforward use cases.
• Practical Use: Real-time updates in live collections are helpful for dynamic DOM changes, like adding or removing classes.

Take It a Step Further

• Experiment with Live Collections: Dynamically modify the DOM to see how the HTMLCollection adjusts in real time.
• Compare Methods: Practice using both getElementsByClassName and querySelectorAll to understand their differences.
• Create Utilities: Build utility functions to combine the benefits of live and static selections for specific use cases.

Practice implementing getElementsByClassName on GreatFrontEnd

9. Memoization in JavaScript: Optimizing Expensive Functions

Memoization is a powerful optimization technique that caches the results of function calls, allowing subsequent calls with the same inputs to return instantly without redundant calculations. It’s a go-to strategy for improving performance in scenarios where functions are repeatedly called with identical arguments.

Example: Memoizing an Expensive Function

Here’s how memoization works in JavaScript with a simple example:

function expensiveOperation(n) {
  console.log('Calculating for', n);
  return n * 2;
}

// Memoization function
function memoize(func) {
  const cache = {};

  return function (n) {
    if (cache[n] !== undefined) {
      console.log('From cache for', n);
      return cache[n];
    } else {
      const result = func(n);
      cache[n] = result;
      return result;
    }
  };
}

const memoizedExpensiveOperation = memoize(expensiveOperation);

console.log(memoizedExpensiveOperation(5)); // Output: Calculating for 5, 10
console.log(memoizedExpensiveOperation(5)); // Output: From cache for 5, 10
console.log(memoizedExpensiveOperation(10)); // Output: Calculating for 10, 20
console.log(memoizedExpensiveOperation(10)); // Output: From cache for 10, 20

How Memoization Works

1. Cache Setup: The memoize function wraps around the original function (expensiveOperation) and creates a cache object.
2. Cache Check: Before executing the original function, memoize checks if the result for a given input already exists in the cache.
3. Cache Hit: If the result is cached, it’s returned immediately without re-executing the function.
4. Cache Miss: If the result isn’t cached, the function is executed, and the result is stored in the cache for future calls.

Why It Matters in Interviews

• Performance Optimization: Demonstrates your ability to reduce computational overhead, an essential skill for optimizing front-end applications.
• Problem Solving: Understanding memoization showcases your grasp of closures, higher-order functions, and caching mechanisms.
• Real-World Relevance: Memoization is widely used in scenarios like recursive algorithms (e.g., Fibonacci, dynamic programming) and heavy computations.

Bonus Insights

• Libraries: Popular libraries like Lodash provide built-in memoization utilities for easy integration.
• Immutable Cache: For more robust implementations, consider using immutable data structures or libraries like Map for better flexibility and performance.
• Edge Cases: Be mindful of inputs that might not cache well, such as non-primitive data types (objects, arrays).

Take It a Step Further

• Advanced Use Cases: Explore memoizing multi-argument functions or asynchronous operations.
• Polyfill Practice: Write your own custom memoization utility to understand the underlying principles.
• Integrate with React: Apply memoization to optimize component rendering and expensive computations in React applications.

Practice implementing Memoize function on GreatFrontEnd

10. Accessing Nested Properties in JavaScript: get and Optional Chaining

Accessing nested properties in JavaScript can sometimes lead to errors if part of the path doesn’t exist. Before optional chaining (?.) was introduced, developers often relied on libraries like Lodash and its get function to safely access deeply nested properties.

The Problem with Nested Access

Consider this example:

const user = {
  name: 'John',
  address: {
    street: '123 Main St',
  },
};

const city = user.address.city; // Throws an error if `address` or `city` is undefined

If any property in the chain (address or city) is undefined, the code will throw an error.

Using get from Lodash

Lodash’s get function simplifies this process by allowing developers to safely retrieve nested properties:

const user = {
  name: 'John',
  address: {
    city: 'New York',
  },
};

console.log(_.get(user, 'address.city')); // 'New York'
console.log(_.get(user, 'address.street')); // undefined

With _.get, you specify the path to the property as a string. If any part of the path doesn’t exist, it safely returns undefined instead of throwing an error.

Modern Alternative: Optional Chaining

JavaScript now has a built-in solution for this problem: optional chaining (?.). It provides a concise way to safely access nested properties:

const user = {
  name: 'John',
  address: {
    street: '123 Main St',
  },
};

const city = user.address?.city; // Returns undefined instead of throwing an error

The ?. operator ensures the evaluation stops if a part of the path is null or undefined, preventing runtime errors.

Why It Matters in Interviews

• Core Problem Solving: Demonstrates your ability to handle undefined or null values effectively in nested data structures.
• Legacy Knowledge: Shows your understanding of older practices like Lodash’s get and their modern replacements.
• Readability and Safety: Using optional chaining simplifies code, reduces errors, and makes it more maintainable.

Bonus Insights

• Default Values: Lodash’s get allows you to specify a default value if the path doesn’t exist:

    _.get(user, 'address.city', 'Unknown'); // 'Unknown'

• Compatibility: Optional chaining is a newer feature, so ensure compatibility if working in environments that don’t fully support ES2020.
• Practical Use: Ideal for handling deeply nested API responses or configurations where not all paths may exist.

Take It a Step Further

• Implement Your Own get Function: Write a custom utility similar to Lodash’s get to deepen your understanding.
• Explore Real-World Scenarios: Practice accessing nested properties in JSON responses from APIs.
• Combine with Nullish Coalescing: Pair optional chaining with the ?? operator for default values:

  const city = user.address?.city ?? 'Unknown';

Practice implementing get function on GreatFrontEnd

Conclusion

These questions delve into essential JavaScript concepts, helping you build a strong foundation to tackle challenging interview problems. Practice thoroughly and be prepared to articulate your thought process while showcasing your code examples with confidence!

👉 Looking for extra support or a clear, effective path to ace your frontend interviews? Explore GreatFrontEnd for expert-designed resources! 🌟 Let’s elevate your coding journey together! 💡