Use postmessage to report, Failed to execute 'postMessage' on' DOMWindow'

use postMessage to send cross-domain messages,
window.postMessage ("hello there messages, location.protocol +" / a.b.com") ;

but the following error was reported: 

Failed to execute "postMessage" on "DOMWindow": The target origin provided ("http://a.b.com") does not match the recipient window"s origin ("http://c.e.com")

what is the reason, please?

Javascript
Mar.23,2021

use event.source as reply object
for more information, please see https://developer.mozilla.org.

. 
//ApostMessagefunctionaddEventListenner
function receiveMessage(event)
{
  // 
  if (event.origin !== "http://example.com:8080")
    return;

  // event.source 
  // event.data  "hello there!"

  // origin (), enent.source
  // event.origintargetOrigin
  event.source.postMessage("hi there yourself!  the secret response " +
                           "is: rheeeeet!",
                           event.origin);
}

window.addEventListener("message", receiveMessage, false);

otherWindow.postMessage (message, targetOrigin, [transfer]);
otherWindow: A reference to other windows , such as the contentWindow property of iframe, the window object returned by window.open, or a named or numerically indexed window.frames.
otherWindow cannot be the current window.
see MDN

.

Previous: Use the onfocus event to change the border color of the input input box, why will it fail when you move the mouse away, and how to change the color as long as the focus is still there?

Next: Regular expression matching problem

css mysql arrays josn react html typescript webpack npm sass R objective-c .net sql-server jquery python-3.x angularjs django angular excel regex iphone ajax linux xml pandas vba spring database wordpress string wpf xcode windows bash postgresql oracle multithreading eclipse list firebase algorithm macos forms image scala visual-studio azure bootstrap spring-boot react-native python-2.7 docker performance function winforms matlab powershell apache dataframe api sqlite numpy rest shell selenium flutter dart maven loops qt swing android-studio csv express file class tensorflow sorting codeigniter perl
MySQL Query : SELECT * FROM `codeshelper`.`v9_news` WHERE status=99 AND catid='6' ORDER BY rand() LIMIT 5
MySQL Error : Disk full (/tmp/#sql-temptable-64f5-1e63553-43fcf.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
MySQL Errno : 1021
Message : Disk full (/tmp/#sql-temptable-64f5-1e63553-43fcf.MAI); waiting for someone to free some space... (errno: 28 "No space left on device")
Need Help?