How in-memory scoping takes place in javascript?

Question

I am aware of lexical scopes, but how scoping takes place in memory.

var val="a";

var func=function(data){
    this.data=data;
    console.log(val+" "+data); // val will be available because it is global.       
    var bar=function(innerData){
        console.log(innerData+" "+val+" "+data);
    }
    bar("inner");

}
func("outer");

but how scopes are defined in memory.

The data is likely stored on the heap, if that's why you mean. — Felix Kling, Dec 07 '15 at 06:14
When you say "how scoping takes place in memory", how technical are you expecting of an answer? — Nick Zuber, Dec 07 '15 at 06:15
Potentially related: http://stackoverflow.com/questions/2800463/how-variables-are-allocated-memory-in-javascript — aug, Dec 07 '15 at 06:17
Check out the link @aug posted - I'm pretty sure it's what you're looking for. — Nick Zuber, Dec 07 '15 at 06:18
I want to know the internals of how in-memory scoping takes place, and answer can be as technical as possible, thanks — Mohd Asim Suhail, Dec 07 '15 at 06:18
I read somewhere that data is stored in form of hash maps, so how does that happens?. — Mohd Asim Suhail, Dec 07 '15 at 06:26
No answer to your question but a wee suggestion for better console living: `console.log([innerData, val, data]);` — Will, Dec 07 '15 at 06:26

score 0 · Answer 1 · answered Dec 07 '15 at 06:20

Every function that's called creates an activation record inside the call stack with all the information withing it (including the address of the variables that are accessible for that scope), and allocating/reserving the slots in memory that it needs. Whenever the function finishes whatever it was doing, the activation record is popped from the stack and the memory freed by removing all the local variables that are being created.

The thing with global variables is that they're declared outside any particular scope or lifetime, so they'll last as long as the program or instance of whatever file its in lasts and will be accesible to anything in the call stack from there on, so that way you'll be able to access val from whatever function you declare below func.

The term *activation record/object* doesn't exist anymore since ES5. — Felix Kling, Dec 07 '15 at 06:22
Are you sure that memory is freed??, if memory is freed then what happens in case of closures? — Mohd Asim Suhail, Dec 07 '15 at 06:22

How in-memory scoping takes place in javascript?

1 Answers1