practiceSheetJS.md

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.

9. 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}

10. 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:

      reverseString("hello"); // "olleh"

12. Count Vowels:

    • Write a function countVowels(str) that counts the number of vowels in a string.
    • Example:

      countVowels("hello world"); // 3

13. Check Palindrome:

    • Create a function isPalindrome(str) that checks if a string is a palindrome.
    • Example:

      isPalindrome("racecar"); // true

14. Remove Whitespaces:

    • Implement removeWhitespaces(str) that removes all spaces from a string.
    • Example:

      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:

      capitalizeWords("hello world"); // "Hello World"

Execution Context and Hoisting Questions

16. 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.

18. Hoisting of Functions:

    • Predict the output:

      greet();
      function greet() {
          console.log("Hello!");
      }

19. 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

26. 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]

27. 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]

28. 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'}

29. 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

30. 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