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β€ŽREADME.md

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@@ -4,7 +4,7 @@ description: "Prepare for your next 2023 JavaScript interview with these tricky
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githubPath: "https://github.com/Vasu7389/JavaScript-Interview-Questions-2023"
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---
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<span style=" font-size: 0.8rem; border-bottom: 1px solid grey;"> Updated Feb 25, 2023 </span>
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<span style=" font-size: 0.8rem; border-bottom: 1px solid grey;"> Updated Mar 11, 2023 </span>
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In this article, we will cover a range of JavaScript interview questions, including those related to the latest versions of the language (ES6, ES7, ES8, and ES9).
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@@ -605,3 +605,289 @@ The `sortStrings` function takes an array of strings as its parameter and uses t
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In the example usage, we pass an array of strings `['apple', 'banana', 'cherry', 'date', 'elderberry']` to the sortStrings function. The function returns a new array with the strings sorted in alphabetical order, which is `['apple', 'banana', 'cherry', 'date', 'elderberry']`.
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</details>
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<details>
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<summary>
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<h3>21. Write a function in JavaScript that checks if a string is a palindrome.
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</h3>
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</summary>
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Answer:
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```js
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function isPalindrome(str) {
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const reversedStr = str.split("").reverse().join("");
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return str === reversedStr;
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}
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// Example usage:
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console.log(isPalindrome("racecar")); // Output: true
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console.log(isPalindrome("hello")); // Output: false
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```
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The `isPalindrome` function takes a string as its parameter and first reverses the string using the `split()`, `reverse()`, and `join()` methods. It then checks if the reversed string is equal to the original string and returns true if they are equal and false otherwise.
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In the example usage, we pass the strings `racecar` and `hello` to the isPalindrome function. The function returns true for the first string because it is a palindrome (i.e., the reversed string is equal to the original string), and false for the second string.
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</details>
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<details>
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<summary>
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<h3>22. Write a function in JavaScript that finds the second highest number in an array of numbers.
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</h3>
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</summary>
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Answer:
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```js
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function findSecondHighest(arr) {
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const sortedArr = arr.sort((a, b) => b - a);
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return sortedArr[1];
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}
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// Example usage:
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const numbers = [10, 5, 20, 15, 8];
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console.log(findSecondHighest(numbers)); // Output: 15
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```
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The `findSecondHighest` function takes an array of numbers as its parameter and first sorts the array in descending order using the `sort()` method and a comparison function. It then returns the second element in the sorted array, which is the second highest number.
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In the example usage, we pass the array `[10, 5, 20, 15, 8]` to the findSecondHighest function. The function returns `15`, which is the second highest number in the array.
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</details>
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<details>
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<summary>
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<h3>23. Write a function in JavaScript that removes duplicates from an array.
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</h3>
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</summary>
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Answer:
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```js
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function removeDuplicates(arr) {
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return [...new Set(arr)];
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}
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// Example usage:
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const numbers = [1, 2, 3, 2, 1, 4, 5, 4];
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console.log(removeDuplicates(numbers)); // Output: [1, 2, 3, 4, 5]
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```
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The `removeDuplicates` function takes an array as its parameter and first creates a Set object from the array using the `Set()` constructor. A Set is a collection of unique values, so all duplicates are automatically removed. We then use the spread syntax `(...)` to convert the Set back to an array.
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In the example usage, we pass the array `[1, 2, 3, 2, 1, 4, 5, 4]` to the removeDuplicates function. The function returns a new array with duplicates removed, which is `[1, 2, 3, 4, 5]`.
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</details>
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<details>
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<summary>
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<h3>24. Write a function in JavaScript that returns the sum of two numbers without using the + operator.</h3>
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</summary>
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Answer:
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```jsx
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function add(a, b) {
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while (b !== 0) {
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let carry = a & b;
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a = a ^ b;
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b = carry << 1;
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}
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return a;
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}
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// Example usage:
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console.log(add(5, 7)); // Output: 12
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```
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The add function takes two numbers a and b as its parameters and uses a bitwise approach to add them. It repeatedly performs a bitwise AND operation between a and b to get the carry bits and performs a bitwise XOR operation between a and b to get the sum bits. It then shifts the carry bits one position to the left and assigns the result to b. This process continues until b is equal to 0. The final value of a is the sum of the two numbers.
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In the example usage, we pass the numbers 5 and 7 to the add function. The function returns 12, which is the sum of the two numbers.
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</details>
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<details>
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<summary>
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<h3>25. Write a function in JavaScript that checks if a given string is a valid IPv4 address.</h3>
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</summary>
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Answer:
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```jsx
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function isValidIPv4(str) {
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const octets = str.split(".");
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if (octets.length !== 4) return false;
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for (let i = 0; i < octets.length; i++) {
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const octet = octets[i];
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if (isNaN(octet) || octet < 0 || octet > 255) return false;
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if (octet.length > 1 && octet[0] === "0") return false;
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}
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return true;
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}
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// Example usage:
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console.log(isValidIPv4("192.168.0.1")); // Output: true
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console.log(isValidIPv4("256.0.0.0")); // Output: false
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```
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The `isValidIPv4` function takes a string as its parameter and checks if it is a valid `IPv4` address.
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An IPv4 address consists of four octets separated by periods, with each octet being a number between 0 and 255.
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The function first splits the string into an array of octets using the split() method.
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It then checks if the array has exactly four elements and if each element is a number between 0 and 255.
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It also checks if each octet does not start with a 0 unless it is a single-digit octet.
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If any of these conditions are not met, the function returns false. Otherwise, it returns true.
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In the example usage, we pass the strings '192.168.0.1' and '256.0.0.0' to the isValidIPv4 function. The function returns true for the first string because it is a valid IPv4 address and false for the second string because it is not a valid IPv4 address.
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</details>
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<details>
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<summary>
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<h3>26. Write a function in JavaScript that converts a given string to title case.</h3>
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</summary>
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Answer:
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```jsx
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function toTitleCase(str) {
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return str.replace(/\b\w+/g, function (word) {
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return word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();
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});
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}
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// Example usage:
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console.log(toTitleCase("the quick brown fox")); // Output: 'The Quick Brown Fox'
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```
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The `toTitleCase` function takes a string as its parameter and converts it to title case. Title case is a style of capitalization where the first letter of each word is capitalized, and the rest of the letters are in lowercase.
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The function uses a regular expression to match the first letter of each word in the string and then uses the `charAt()` and `slice()` methods to capitalize the first letter and convert the rest of the letters to lowercase. It returns the modified string.
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In the example usage, we pass the string 'the quick brown fox' to the toTitleCase function. The function returns 'The Quick Brown Fox', which is the string converted to title case.
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</details>
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<details>
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<summary>
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<h3>27. Write a function in JavaScript that generates a random hexadecimal color code.</h3>
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</summary>
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Answer:
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```jsx
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function getRandomColor() {
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const hexChars = "0123456789ABCDEF";
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let color = "#";
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for (let i = 0; i < 6; i++) {
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color += hexChars[Math.floor(Math.random() * 16)];
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}
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return color;
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}
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// Example usage:
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console.log(getRandomColor()); // Output: e.g. '#3D5A89'
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```
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The `getRandomColor` function generates a random hexadecimal color code. A hexadecimal color code is a six-digit code that represents a color by specifying the amount of red, green, and blue in it.
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Each digit of the code can be any of the sixteen hexadecimal characters (0 to 9 and A to F).
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The function generates a random color code by selecting six random hexadecimal characters from the hexChars string using the Math.random() function and concatenating them together with a # symbol.
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It then returns the generated color code.
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In the example usage, we call the getRandomColor function, which returns a randomly generated color code. The output can vary each time the function is called, but it should be a valid hexadecimal color code.
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</details>
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<details>
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<summary>
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<h3>28. Guess the output of the following code:</h3>
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```jsx
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let x = 5;
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{
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let x = 10;
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console.log(x);
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}
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console.log(x);
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```
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</summary>
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The output of the code above is:
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Answer:
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```bash
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10
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5
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```
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This is because of the block scoping behavior of the let keyword in ES6.
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When we declare a variable with `let` inside a block (in this case, the block is defined by the curly braces), the variable is only accessible inside that block and its sub-blocks.
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In the code above, we define a variable `x` outside the block with the value of `5`. Then we define another variable x inside the block with the value of 10.
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The first `console.log()` statement inside the block will print 10, because x refers to the variable defined inside the block. The second console.log() statement outside the block will print 5, because it refers to the variable defined outside the block.
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</details>
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<details>
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<summary>
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<h3>29. Guess the output of the following code:</h3>
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```jsx
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const obj = { a: 1, b: 2, c: 3 };
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const { a, b } = obj;
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console.log(a, b);
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```
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</summary>
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The output of the code above is:
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Answer:
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```bash
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1 2
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```
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This is because of the object destructuring syntax introduced in ES6.
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We declare a constant variable obj with an object containing three properties. Then we use object destructuring to extract the properties a and b from the object and assign them to separate variables with the same names.
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The console.log() statement then prints the values of the a and b variables, which are 1 and 2 respectively.
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</details>
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<details>
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<summary>
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<h3>30. Guess the output of the following code:</h3>
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```jsx
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const arr1 = [1, 2, 3];
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const arr2 = [4, 5, 6];
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const arr3 = [...arr1, ...arr2];
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console.log(arr3);
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```
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</summary>
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The output of the code above is:
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Answer:
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```bash
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[1, 2, 3, 4, 5, 6]
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```
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This is because of the spread syntax `(...)` introduced in ES6.
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The `...` operator can be used to spread the elements of an array or the properties of an object into a new array or object.
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In the code above, we define two arrays arr1 and arr2. Then we create a new array arr3 by spreading the elements of arr1 and arr2 into it using the spread syntax.
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The console.log() statement then prints the contents of arr3, which are the elements of arr1 followed by the elements of arr2.
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</details>

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