How do you use window postMessage across domains

Question

It seems like the point of window postMessage is to allow safe communication between windows frames hosted on different domains  but it doesn t actually seem to allow that in Chrome   Here s the scenario      Embed an  lt iframe gt   with a src on domain B   in a page on domain A  The  lt iframe gt  ends up being mostly a  lt script gt  tag  at the end of which s execution    I call window postMessage  some data  page on A     The  lt iframe gt  is most definitely in the context of domain B  and I ve confirmed that the embedded javascript in that  lt iframe gt  executes properly and calls postMessage with the correct values   I get this error message in Chrome        Unable to post message to A    Recipient has origin B    Here s the code that registers a message event listener in the page on A   window addEventListener     message     function  event           Do something        false     I ve also tried calling window postMessage some data        but all that does is suppress the error   Am I just missing the point here  is window postMessage      not meant for this   Or am I just doing it horribly wrong    Mime-type text html  which it must remain

User · Answer

Probably you try to send your data from mydomain com to www mydomain com or reverse  NOTE you missed  www   http   mydomain com and http   www mydomain com are different domains to javascript

User · Answer

Here is an example that works on Chrome 5 0 375 125   The page B  iframe content     lt html gt       lt head gt  lt  head gt       lt body gt           lt script gt              top postMessage  hello    A             lt  script gt       lt  body gt   lt  html gt    Note the use of top postMessage or parent postMessage not window postMessage here  The page A    lt html gt   lt head gt  lt  head gt   lt body gt       lt iframe src  B  gt  lt  iframe gt       lt script gt          window addEventListener   message             function  e                    if e origin      B    return                     alert e data                          false        lt  script gt   lt  body gt   lt  html gt    A and B must be something like http   domain com  EDIT   From another question  it looks the domains A and B here  must have a   for the postMessage to work properly

User · Answer

You should post a message from frame to parent  after loaded   frame script     document  ready function         window parent postMessage  I m loaded               And listen it in parent   function listenMessage msg        alert msg      if  window addEventListener        window addEventListener  message   listenMessage  false     else       window attachEvent  onmessage   listenMessage       Use this link for more info  http   en wikipedia org wiki Web Messaging

[javascript] How do you use window.postMessage across domains?

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