How To Adopt The Change?
So, in short, to adopt the change quicker, start with the basic principles of programming languages. Because today languages change their features like weather, but if you have knowledge of the basic concept of the language. Then, no change can affect you in any way.
Go With The Old
let and const Behaves Differently Than var
Variable declarations with var were always hoisted to the top of their containing scope by default, regardless of where they were placed inside of that scope. That meant that even a deeply nested variable could be considered declared and available right from the beginning of its containing scope. The same is not true of let or const.
Traditionally function is used to define the function keyword, the extension area of the function can be varied. It can be also used with the new keyword to constrict the objective with the prototypal inheritance. Functions defined in both types can be called before and after the declaration.
New Arrow Function