10 Common JavaScript Interview Questions (and Answers)

1. Find the frequency of elements in array

Method 1: Using Reduce method of array

Method 2: Using an Object

2. Group items on the basis of age of given array of object

3. Program to check a string with balanced brackets.

4. Find the pairs of array element for which sum is equal to given target value (Two Sum Problem)

5. Find the missing number from unsorted array with O(n) complexity

Algorithm

1. Create a variable sum = 1 which will store the missing number and a counter variable c = 2.
2. Traverse the array from start to end.
3. Update the value of sum as sum = sum — array[i] + c and update c as c++.
4. Print the missing number as a sum.

6. Find the missing number from sorted array with O(n) complexity

7. Find the nth largest element in a sorted array

8. Remove duplicates from an array and return unique values in O(n) complexity.

9. Print all duplicate elements of an array

10. Collect books from array of objects and return collection of books as an array

I hope you have found this quick list of common JavaScript interview questions and answers useful. Thank you for reading!

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