Make variables live inside interface??

Question

I'm trying to modify a variable which is outside the interface method
Reference
index.js
let myVar = ``;
let query = Someclass.method( e => {
myVar = e.data();
return;
});
Console.log(myVar);
And if you can't understand my question please ask me

Answer 1

Ja Play Sorry Dude, it's in living in my localhost and there is no Playground alone for node and js
If you can really help I'll git

Answer 2

Can you show your attempt on playground where you have a problem?