Difference between this.var; vs let var; in JavaScript?

Question

//in JavaScript OOP
//in know about the new 'Class' in es6 still need to clear fundamentals

let Cname = function(){
this.prop1 = "some val";
let prop2 = "other val";
}

//what is the difference between the above variables or is it a good practice or not

Answer 1

"this" is a reference variable, it refers to the object the Cname belongs to. Here right now Cname belongs to the window object that is a global object..
As soon as you instantiate an object of the Cname, then this will point to that object..

for ex :
let obj = new Cname();
now "prop1" and "prop2" points to the "obj" object.

or if you just call:

Cname();
then the "prop1" and "prop2" belongs to the window object.

And "let/const" are another way to define variable, but if you create a variable with "var/let/const" locally you cannot directly use it globally or outside that block

so we use "this" on purpose, when we need to create objects or have dynamic usage..

otherwise we always use "let" and "const"

Answer 2

It's not about best, it's about what to need to use.

When you want to define something as property of that class or constructor function you use 'this' and let/const for normal variables.
https://code.sololearn.com/WkSGhPmj9uB6/?ref=app