Getting the document object of an iframe

This is the code I use:

var ifrm = document.getElementById('myFrame');
ifrm = (ifrm.contentWindow) ? ifrm.contentWindow : (ifrm.contentDocument.document) ? ifrm.contentDocument.document : ifrm.contentDocument;
ifrm.document.open();
ifrm.document.write('Hello World!');
ifrm.document.close();

contentWindow vs. contentDocument

• IE (Win) and Mozilla (1.7) will return the window object inside the iframe with oIFrame.contentWindow.
• Safari (1.2.4) doesn't understand that property, but does have oIframe.contentDocument, which points to the document object inside the iframe.
• To make it even more complicated, Opera 7 uses oIframe.contentDocument, but it points to the window object of the iframe. Because Safari has no way to directly access the window object of an iframe element via standard DOM (or does it?), our fully modern-cross-browser-compatible code will only be able to access the document within the iframe.

Try the following

var doc=document.getElementById("frame").contentDocument;

// Earlier versions of IE or IE8+ where !DOCTYPE is not specified
var doc=document.getElementById("frame").contentWindow.document;

Note: AndyE pointed out that contentWindow is supported by all major browsers so this may be the best way to go.

• http://help.dottoro.com/ljctglqj.php

Note2: In this sample you won't be able to access the document via any means. The reason is you can't access the document of an iframe with a different origin because it violates the "Same Origin" security policy

• http://javascript.info/tutorial/same-origin-security-policy

For even more robustness:

function getIframeWindow(iframe_object) {
  var doc;

  if (iframe_object.contentWindow) {
    return iframe_object.contentWindow;
  }

  if (iframe_object.window) {
    return iframe_object.window;
  } 

  if (!doc && iframe_object.contentDocument) {
    doc = iframe_object.contentDocument;
  } 

  if (!doc && iframe_object.document) {
    doc = iframe_object.document;
  }

  if (doc && doc.defaultView) {
   return doc.defaultView;
  }

  if (doc && doc.parentWindow) {
    return doc.parentWindow;
  }

  return undefined;
}

and

...
var el = document.getElementById('targetFrame');

var frame_win = getIframeWindow(el);

if (frame_win) {
  frame_win.targetFunction();
  ...
}
...