Acheron Software Consultancy

1. Write a function that takes a string as input and returns a boolean indicating whether the string contains properly closed braces.

2. Given an array of integers, find the first duplicate number. That is, find the first number that occurs more than once in the array. If no duplicates exist, return -1.

3. What is the use of ViewChild with the static flag set to false or true?

4. How can you handle sending multiple requests to the backend simultaneously?