Full Stack Engineer

• What is the difference between var, let, and const variables? (Learn)
• Define closures with an example. (Learn)
• Write code for handling promises in JavaScript.
• Write code for fetching data from an API using the fetch() method.
• Explain JWT in detail. (Learn)
• What is middleware? (Learn)
• Explain the Virtual DOM. (Learn)
• How do you manage state in React.js? (Learn)
• Explain hooks and why we use them instead of class-based components.
• Write code for useEffect and useState hooks.
• Explain the flow of Redux. (Learn)

Write a function that will take an integer n as a parameter. You need to create two lists, one for odd numbers and one for even numbers between 1 and n, and print them using JavaScript.

• Explain tokens and authentication.
• How do you use .populate() and findOne() in MongoDB?
• Explain aggregation in MongoDB. (Learn)
  
   

1. var x = 10;
let y = 20;
const z = 30;
if (true) {    
var x = 100; // What happens to x?
let y = 200; // What happens to y?
const z = 300; // What happens to z?
}
console.log(x, y, z);

2. console.log('Start');
setTimeout(() => console.log('middle'), 0);
console.log('End');

function outer() {
   let count = 0;
   return function inner() {
       count++;
       return count;
   };
}
const counter = outer();
console.log(counter()); // Output?
console.log(counter()); // Output?

1. console.log(5 == '5'); 
   console.log(5 === '5');
2. let a= ["1","2"], let b=["1","2"]
   console.log(a==b)
3. let a=2, let b=2
   console.log(a==b)
4. let a=["1","2"];
   let b=a;
   b.push("3");
   console.log(a,b)
5. const numbers = [1, 2, 3];
   const doubled = numbers.map(num => num * 2);
   console.log(doubled);