Pergunta de entrevista da empresa LTIMindtree

Basic JS question 1. Difference between let,const,var 2. Callback? and write an example 3. Promises? Example and what is promise.all ? Example with code 4. What are middleware? Tell the architecture how you implement an authentication system with jwt refresh keys and access keys 5. DSA - Find the First Missing Positive number from an array Solved it using hash map in TC - O(n) and SC -O(n). But couldn't optimise it to TC -O(n) and no extra space. 6. Design a parking Lot