How do I implement postMessage() in JavaScript?

Question

I need help with the window.postMessage method. I'm trying to post a message to an iframe from the parent window.

The iframe's name and ID is myFrame, and I have tried the following code, with no avail:

document.getElementById('myFrame').contentWindow.postMessage('Hello','*')

Are the pages on the same domain? Otherwise you're going to be running into XSS security issues and quite likely the reason it's not working. — kieran
– kieran, Commented Jan 16, 2011 at 16:39
@kieran I was looking for a cross-domain communication and I found this as the best way after almost 2 days of googling :- developer.mozilla.org/en/dom/window.postmessage — sreejith
– sreejith, Commented Jan 16, 2011 at 16:47
What error did it give you? Just "it's not working" is not specific enough. — Thai
– Thai, Commented Jan 16, 2011 at 16:58
@Thai no error is being produced in the console, it's left blank!! — sreejith
– sreejith, Commented Jan 16, 2011 at 17:04
A bit OT, but there are some very good ways of doing cross domain/frame communication that doesn't use window.postmessage, try to look here for inspiration: softwareas.com/cross-domain-communication-with-iframes — Martin Jespersen
– Martin Jespersen, Commented Jan 16, 2011 at 18:46

meder omuraliev · Accepted Answer · 2011-01-16 16:39:41Z

1

Take a step back and debug.

What does document.getElementById('myIframe') give you?
What does document.getElementById('myIframe').contentWindow give you?
Do you have a global method named postMessage in the iframe?
Is the iframe domain the same as the initial page? It has to be.
Does the browser throw any errors in the console?

answered Jan 16, 2011 at 16:39

meder omuraliev

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2 Comments

Mattio Over a year ago

The iframe does not have to be on the same domain for window.postMessage.

Zach Over a year ago

Mattio is correct, the iframe does not have to be on the same domain. I've run into this problem as well and it seems the problem lies in that document.getElementById('myFrame').contentWindow returns undefined.

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