Javascript postMessage loses Class Instance Properties

Started by Heretic86, April 27, 2021, 07:42:29 pm

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Hopefully this is an "easy" one.

I have a page that creates an Instance of a Class.  Then the Class Instance is sent to another page using page.postMessage();  When I receive the data on the other page, and I check the received data to see if the object is an Instance of the Class, it always fails, presumably because I am missing a step.

Properties Page:
class MyClass {
  constructor(name, value){ = name;
    this.value = value;
const foo = new MyClass("bob", 123);
window.postMessage( { myMsg : foo });
function messageListener(msg){
  console.log( instanceof MyClass); // Always returns false

I left a lot of code out of the examples but basically using Modules so the same class constructor is available on both pages.

I would like to be able to check the data on the receiving page to see if the object is an instance of the class.

What am I doing wrong?  Most importantly, how can I check on the receiving page to see if the received data is an instance of the class?
Current Scripts:
Heretic's Moving Platforms

Current Demos:
Collection of Art and 100% Compatible Scripts

(Script Demos are all still available in the Collection link above.  I lost some individual demos due to a server crash.)


Try printing just:


to see if you actually have the proper data/object inside.
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