The concept of scope is quite easy and very important topic in javascript. So let's delve deeper into this issue. Scope is the ability of our other code pieces to access this value or not, depending on where the variable defined is located. In other words, we can access variables, objects, functions according to their scope...
This keyword is the scariest part of JavaScript. Yes, this is one of the most confusing topics so why is this confusing? because its value can sometimes seem unpredictable. There are rules that determine the value of this structure, and once we learn these rules, the concept of this will not confuse us.
Callbacks are functions passed to other functions to be called inside the outer function. it is any function called by another function using a parameter. when we pass a function to another function and it is executed in that function, we can call it a callback.