66

script of iframe

<script type="text/javascript" >
var a=5;
</script>

script of parent window

<script type="text/javascript" >
function close()
{
var check=document.getElementById("iframeid").contentDocument.a;
alert(check)
}
</script>

I want to access the variable which is defined inside the iframe from parent. But the above code doesn't work properly can anyone give an idea to implement this.

Mirchi
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6 Answers6

68

Using contentWindow instead of contentDocument works for me:

var check = document.getElementById("iframeid").contentWindow.a;

Also, ensure that the domains match and that you are using a webserver to test (I got a protocol warning when testing from the file system).

UPDATE: You're almost definitely better to use the postMessage API.

Lee Gunn
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  • Chrome: SecurityError: Blocked a frame with origin "http://mydomain.com" from accessing a cross-origin frame. – Yevgen Nov 22 '13 at 23:44
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    @Yevgen: you have Access-Control-Allow-Origin set up for the same origin set up. If you need information from the parent window look up postMessage and create a message event listener. – jnoreiga Dec 10 '15 at 17:08
  • http://stackoverflow.com/questions/3457391/how-do-you-use-window-postmessage-across-domains – jnoreiga Jun 01 '16 at 13:24
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    this throws error `Uncaught DOMException: Blocked a frame with origin "http://localhost:8000" from accessing a cross-origin frame.` I'm on django dev server on my laptop. – Rishabh Agrahari Aug 28 '17 at 08:15
  • You cannot access an object or variable from the iframe with this method only DOM elements – lisandro Feb 03 '22 at 16:03
21

One method that has always worked reliably for me is for the iFrame to give its parent a reference to its own window when it first loads. The parent can then access all the variables through that reference. This does require that the parent is loaded before the iFrame, but for me that is usually the case.

So in the parent 

var iFrameWin;

Then in the iFrame at some point after it has loaded and settled down

parent.iFrameWin = window;  //parent now has a ref to the iframe's window

Then, in the parent when it wants a global var contents from the iFrame

alert(iFrameWin.ivar);  // shows value if the global 'ivar' in the iFrame
John Page
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7

script of iframe:

var a = 5;
window.parent.postMessage(['varA', a], '*'); // put this in some sort of function, ready, or whatever - you can call it multiple times if you need to as the code in the parent is an eventListener

script of parent window:

var b;
// you might want to write these into if statements to make sure that e.data[0] is varA if you have multiple messages coming across
if (typeof window.addEventListener != 'undefined') {
    window.addEventListener('message', function(e) {
        b = e.data[1];
    }, false);
} else if (typeof window.attachEvent != 'undefined') { // this part is for IE8
    window.attachEvent('onmessage', function(e) {
        b = e.data; // you'll probably have to play around with this part as I can't remember exactly how it comes across in IE8 -- i think it will involve slice() iirc
    });
}

Most of my knowledge on this topic comes from Ben Vinegar's talk on Seamless iFrames

This is a cross-domain "okay" method to deal wit this stuff. I'm sure there are some security holes, just as with anything on the web.

greg5green
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    Men you saved me after hours, I did find a solution with postMessage but didn't know passing `'*'` from iframe as domain name will work for file:/// in chrome – Pawel Cioch Feb 02 '18 at 19:39
3

See if this works for you:

i created this parent.html page and put an iframe in it with a text input which will show the value passed from iframe window:

 <html>
     <head>
     <title>IFrame Example</title>
     <script language="javascript">
          function hello(string){
               var name=string
               document.getElementById('myAnchor').value=name;
           }
     </script>
     </head>
     <body>
         <iframe namne="iframe" id="iframe_id" src="inputForm.html" height="150" >
         </iframe>
         Name: <input type="text" id="myAnchor" >
         </body>
</html>

and this iframe content page:

<html>
   <head>
   <title>IFrame Child Example</title>
   </head>
   <body>
   <form name="frm2" >
      <h1><font color="#000099">Input Form</font></h1>
      <p>Name : </p><input type="text" name="resp" id="input" value=""/>
      <input type="button" onclick="parent.hello(this.form.resp.value);" value="Submit" />
   </form>
 </body>
</html>

clicking the button i get the value in my parent window.

Play with it if you get something with this one.

Jai
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1

document.getElementById('ID_OF_IFRAME').document.getElementById('f1')

Note that cross-domain restrictions will still apply.

Osiris
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1

This is how SharePoint do it when passing argument values from the parent window to the iframe. It's simple, but it works.

<html>
<body>
  <iframe id="iframe1"></iframe>
  <script type="text/javascript">
    var ifr = window.document.getElementById("iframe1");
    ifr.dialogArgs = "Hello from the other side.";
    ifr.src = "iframeContent.html"
  </script>
</body>
</html>

Inside iframeContent.html:

<html>
<body>
    <input type="button" value="Click Me!" onclick="alert(window.frameElement.dialogArgs);" />
</body>
</html>

The other way around (accessing ifr.dialogArgs from the parent window after having its value modified by the iframe document) also works.

Vinicius
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