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Array Questions

1. Reverse Array:

  • Write a function reverseArray(arr) that takes an array as input and returns a new array with elements in reverse order.

2. Remove Duplicates:

  • Create a function removeDuplicates(arr) that removes duplicate elements from an array and returns a new array.
  • Example: 
    removeDuplicates([1, 2, 2, 3, 4, 4]); // [1, 2, 3, 4]

3. Find Maximum:

  • Write a function findMax(arr) that returns the largest number in an array.
  • Example: 
    findMax([4, 1, 7, 3]); // 7

4. Sum of Elements:

  • Implement sumArray(arr) to return the sum of all elements in an array.
  • Example: 
    sumArray([1, 2, 3]); // 6

5. Flatten Nested Arrays:

  • Write a function flattenArray(arr) that flattens a nested array into a single-level array.
  • Example: 
    flattenArray([1, [2, [3, 4]]]); // [1, 2, 3, 4]

Object Questions

6. Merge Two Objects:

  • Create a function mergeObjects(obj1, obj2) that merges two objects.
  • Example: 
    mergeObjects({a: 1}, {b: 2}); // {a: 1, b: 2}

7. Count Properties:

  • Write a function countProperties(obj) that returns the number of properties in an object.
  • Example: 
    countProperties({a: 1, b: 2}); // 2

8. Deep Clone an Object:

  • Implement deepClone(obj) that creates a deep copy of the given object.

  1. Filter Object by Keys:

    • Write a function filterByKeys(obj, keys) that returns a new object containing only the specified keys from the original object.
    • Example: 
      filterByKeys({a: 1, b: 2, c: 3}, ['a', 'c']); // {a: 1, c: 3}

  2. Swap Keys and Values:

    • Write a function swapKeysAndValues(obj) that swaps the keys and values of an object.
    • Example: 
      swapKeysAndValues({a: 1, b: 2}); // {1: 'a', 2: 'b'}

String Questions

11. Reverse String: - Create a function reverseString(str) that returns the reversed version of a given string. - Example: javascript reverseString("hello"); // "olleh"

12. Count Vowels: - Write a function countVowels(str) that counts the number of vowels in a string. - Example: javascript countVowels("hello world"); // 3

13. Check Palindrome: - Create a function isPalindrome(str) that checks if a string is a palindrome. - Example: javascript isPalindrome("racecar"); // true

14. Remove Whitespaces: - Implement removeWhitespaces(str) that removes all spaces from a string. - Example: javascript removeWhitespaces("hello world"); // "helloworld"

15. Capitalize Every Word: - Write a function capitalizeWords(str) that capitalizes the first letter of every word in a string. - Example: javascript capitalizeWords("hello world"); // "Hello World"

Execution Context and Hoisting Questions

  1. Predict Output:
    • What will be the output of the following code? 
      console.log(a);
var a = 10;
    • Explain why.

17. Scope Example: - Write a function checkScope() to demonstrate how let, var, and const behave differently inside a block scope.

  1. Hoisting of Functions:

    • Predict the output: 
      greet();
function greet() {
    console.log("Hello!");
}

  2. Hoisting with let and var:

    • Write a short code example showing how let and var differ in terms of hoisting.

20. Temporal Dead Zone: - Explain the concept of Temporal Dead Zone with an example using let and const.

Variable Declaration Questions

21. Reassign let, var, and const: - Write code that demonstrates reassigning values to let, var, and const, and explain the outcomes.

22. Variable Shadowing: - Create an example showing variable shadowing using let and var.

23. Global Scope vs Local Scope: - Write code to explain the difference between global and local scopes using var, let, and const.

24. Block Scope with let: - Create an example that demonstrates block scoping with let.

25. Differences between var, let, and const: - Write a code snippet that highlights the key differences between these variable declarations.

Higher-Order Function Questions

  1. Use map to Transform Array:

    • Write a function doubleNumbers(nums) that doubles each number in the array using map.
    • Example: 
      doubleNumbers([1, 2, 3]); // [2, 4, 6]

  2. Use filter to Remove Falsey Values:

    • Create a function filterFalsey(arr) that removes all falsey values from an array using filter.
    • Example: 
      filterFalsey([0, 1, false, 2, "", 3]); // [1, 2, 3]

  3. Find Object in Array:

    • Write a function findUser(users, name) that uses find to return the user object matching the given name.
    • Example: 
      findUser([{name: 'Alice'}, {name: 'Bob'}], 'Bob'); // {name: 'Bob'}

  4. Use reduce to Sum Array Elements:

    • Write a function sumArray(nums) that returns the sum of numbers in an array using reduce.
    • Example: 
      sumArray([1, 2, 3, 4]); // 10

  5. Check All Even Numbers using every:

    • Write a function allEven(nums) that checks if all elements in an array are even using every.
    • Example: 
      allEven([2, 4, 6]); // true
allEven([1, 2, 3]); // false