Mastering JavaScript: 10 Tricky Interview Questions on Arrays and Objects
Tags: javascript, interview
Published: 2024-02-17 18:36:50

**Introduction:**

Welcome, fellow developers! In the realm of JavaScript interviews, navigating questions on arrays and objects requires a solid understanding of the language's nuances. In this blog post, we'll delve into 10 tricky interview questions, aiming for clarity and mastery rather than humor. Let's sharpen those coding skills!

---

**1. The Swapping Saga:**
*Question:* How can you swap the values of two variables without using a temporary variable?

*Answer:* Utilize destructuring assignment for an elegant swap:
```javascript
let a = 42, b = 24;
[a, b] = [b, a];
```
The values exchange places seamlessly.

---

**2. Object Overhaul:**
*Question:* Explain the process of cloning an object in JavaScript.

*Answer:* Employ the spread operator for a simple object duplication:
```javascript
const originalObj = { one: 1, two: 2 };
const clonedObj = { ...originalObj };
```
Cloning accomplished without complication.

---

**3. Array Amalgamation:**
*Question:* How do you eliminate duplicates from an array?

*Answer:* Leverage the Set data structure to effortlessly remove duplicates:
```javascript
const arrayWithDupes = [1, 2, 3, 1, 2, 4];
const noDupesArray = [...new Set(arrayWithDupes)];
```
Duplicates vanish, leaving a pristine array.

---

**4. The Palindrome Puzzle:**
*Question:* Write a function to determine if a string is a palindrome.

*Answer:* Craft a function using array methods:
```javascript
function isPalindrome(str) {
  const reversed = str.split('').reverse().join('');
  return str === reversed;
}
```
A reliable palindrome detector.

---

**5. Object Inquiry:**
*Question:* How can you check if an object contains a specific property?

*Answer:* Employ the "in" operator for a straightforward property check:
```javascript
const myObject = { name: 'JavaScript', age: 25 };
const hasProperty = 'age' in myObject;
```
A simple inquiry confirms the property's existence.

---

**6. Array Append:**
*Question:* Add an element to the end of an array.

*Answer:* Utilize the push() method for seamless array expansion:
```javascript
const array = ['apple', 'banana', 'cherry'];
array.push('date');
```
Effortless appending at the array's end.

---

**7. The NaN Dilemma:**
*Question:* How do you determine if a value is NaN?

*Answer:* Use Number.isNaN() to accurately identify NaN:
```javascript
const mysteriousValue = NaN;
const isItNaN = Number.isNaN(mysteriousValue);
```
A reliable check for the elusive NaN.

---

**8. Object Fusion:**
*Question:* Merge two objects into one.

*Answer:* Utilize the spread operator for a smooth object fusion:
```javascript
const obj1 = { a: 1, b: 2 };
const obj2 = { c: 3, d: 4 };
const fusedObject = { ...obj1, ...obj2 };
```
Objects combine forces seamlessly.

---

**9. The Filtering Feat:**
*Question:* Remove falsy values from an array.

*Answer:* Deploy the filter() method to sift out falsy elements:
```javascript
const questionableArray = [0, false, '', null, undefined, 42];
const truthArray = questionableArray.filter(Boolean);
```
False values eliminated, leaving truth behind.

---

**10. The Lost Element:**
*Question:* Find the missing number in an array of consecutive integers.

*Answer:* Utilize the sum formula to deduce the missing number:
```javascript
const detectiveArray = [1, 2, 3, 5, 6];
const missingNumber = 15 - detectiveArray.reduce((sum, num) => sum + num, 0);
```
A mathematical approach unveils the missing integer.

---

Bravo! You've navigated through these JavaScript intricacies. These questions and answers are designed to hone your understanding of arrays and objects, ensuring you're well-prepared for any interview challenge. Happy coding!