How do I Get variable from a parent webpage Construct game inside IFRAME?

I have my game embedded in an iFrame on a PARENT webpage and I

need to get a variable from the PARENT webpage into my construct game that

lives inside an iFrame on the PARENT webpage?

Here is a concept drawing.

My game LIVES within an iFrame on a PARENT web page.

I need to READ several variables that exist within the PARENT web page

into the iFrame Construct game inside an iFrame.

All the posts seem to assume a game has an iFrame within the game.

My game will exist inside an iFrame on a PARENT web page.

You can try this with the C3 script feature

developer.mozilla.org/en-US/docs/Web/API/Window/postMessage

H Eren,

Thank you very much for the post..

So, this example I found doesn't seem to work.

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In PARENT web page:

 var my_var = 'hello world!';

 function some_fn()
 {
 alert(parent.my_var); //hello world!
 }

The following returns a 0 value, it should return a string value of "hello world!"