How do I receive a Postmessage inside construct?

I have my game hosted in an iframe inside a page. The parent page needs to pass a token to the game. I have the parent page send a post message to the gamewindow. Inside construct, would this code be an eventscript made inside the eventsheet or is it a browser javascript action or is it a script to be added to the scripts folder under main.js ?

window.addEventListener("message", (event) => {

if (event.origin !== "http://example.org:8080")

return;

// ...

}, false);

Also, since the game runs in a worker, would window.addeventlistener work?

Bumping this. If the parent webpage is sending a message to the iframe with the game in it, how do I read the message inside construct? Is it through a browser.execjs event or a eventsheet inline js? Is there an example somewhere I can take a look at?

Thanks in advance for the help.

This is what I do right now, is this right? This is an eventsheet add script section.

Ashley - Can you help me with this?

Adding a script file with the original code should work. Listening for the "message" event on window is the correct approach.

The differences are documented in the manual: see scripts in event sheets and script files.

Based on this, a script as eventsheet action the way I have it in the screenshot should work right?

You should only add the event listener once. I can't see from the screenshot whether the event blocks do that. It would probably be best to add it in a script file, because even if it's under 'On start of layout', it could still add the listener multiple times if you keep revisiting the layout.

Yup! That makes a lot of sense. Thanks. One last question - If I were to put the listener at runOnStartup and set the message to a globalvar, on startup, globalvar might not have been initialized right? Or should I create a global var in script and then use it later in eventsheets?

Turn off worker mode. Otherwise your script is running in a worker, not the window, so won't receive messages to the window.

Solved this! In case someone stumbles upon this - What was happening was the postmessage was getting sent before construct had a chance to add event listener. Sometimes the eventlistener was added in time to catch the message, sometimes it was not. I extended the timeout of the postmessage and added a boolean flag to wait for the event to be caught before the loader moved to the next layout. Works fine now. Thanks Ashley for the help.