'message' event handler running in an iframe is not receiving the data sent by the `postMessage` call

What is your Scenario?

The SUT is using postMessage from within a custom polymer web component to send data to a hidden iframe.

What is the Current behavior?

The message object that is received by the ‘message’ event handler has it’s data field set to undefined (as is it’s origin field)

What is the Expected behavior?

The ‘message’ event handler running within the iframe should receive a message object with it’s data field set to the object that was supplied by the postMessage call

Your complete app code (or attach your test files):

// polymer web component running in the parent top level window:
const configs = { configuration: 'some_important_value' };
this.$.auth.contentWindow.postMessage(configs, '*');

// (okta-auth.js) event handler for the posted message running in the iframe
window.addEventListener('message', function(e) {
  // this line fails as `data` field is undefined
  if(e.data.configuration) {
    // do stuff with the e.data.configuration
  }
});

// test file
import { Selector } from 'testcafe';

fixture`Test Welcome page`
  .page`http://localhost:53660`;


test('When I navigate to the welcome page do I see the Application Gateway bar?', async t => {
  await t
    .wait(10000)
    .typeText('#ClientID', 'P123456')
    .click('#GoButton')
    .typeText('#okta-signin-username', '[e-mail]')
    .typeText('#okta-signin-password', 'xxxxxxxx')
    .click('#okta-signin-submit')
    .wait(15000)
    .expect(Selector('application-gateway-app').exists).ok();
});

Screenshots:

Your Environment details:

• node.js version: v10.15.3
• browser name and version: Chrome 75
• platform and version: Windows 10 1803

[miherlosev]

Hi @amal-architrave

To correctly raise an event you need to call 3 methods in sequence:

• document.createEvent
• event.initEvent
• window.dispatchEvent

For more information, see the Creating and triggering events topic.

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