Discuss the scope of `var`, `let`, and `const`

All of these is used to assing variable in javascript.But each of them there own identity, good side and side Effect.

Var - It's a global scop which help to assing, update, and access over the script.It act likely .this method in Javascript. The down side of this is can create conflict between variable whos have same name inside the script.

Let & Const inreduces during Javascript ES6 indroducton. Both counterd the dowside of Var. Both create a local scop wich can't get accesss acrosse the script

Let - is muteable but Cont immuteable & cant update value once assinged

Tell us the use cases of `null` and `undefined`

In javascript both indicates a variable or object has no value. But both has diffent usecases.

Null - This mainly means that variable has created intensionaly for, in future value might be assing.

Undefined - Indicates a variable that has been declared but not yet assigned a value.

What do you mean by REST API?

REST API - This an Architectural style to comonicate with endpoint to endpoint to transferr, retrive data & information.

REST -Representational State Transfer: It's describes the general rules for how the data and services are represented through the API so that other programs will be able to correctly request and receive the data and services that an API makes available.

API - Application Programming Interface : Used to transfer data throwout application and server in various format.