Local Storage Vs. Session Storage

Session Storage: The sessionStorage object stores data only for a session. It means that the data stored in the sessionStorage will be deleted when the browser is closed.

Local Storage: Unlike sessionStorage localStorage continues to store data after the browser is closed. It means that data stored in localStorage does not expire.

Global Scope Vs. Block Scope

Scope: Visibility or Accessibility of a variable.

Global Scope: If a variable is declared outside all functions or curly braces ({ ... }), it is said to be defined in the global scope. Once you’ve declared a global variable, you can use that variable anywhere in your code, even in functions.

Block Scope: When you declare a variable with const or let within a curly brace ({ ... }), you can access this variable only within that curly brace.

What is Event Loop?

Event Loop: It's a fundamental piece of the JavaScript engine that always monitor call stack, task queue and microtask queue. If the call stack is empty it puts callback function in call stact from task queues.

When do we get undefined in JavaScript?

1. When try to accessing an uninitialized variable.
2. When a function does not return anything it return undefined.
3. When you try to access a property of an object that does not exist.
4. When try to accessing out-of-bounds array elements.