javascript - what is this window.top check performing? is this checking for an iframe? - Stack Overflow

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if(window.top!==window.self){document.write="";
window.top.location=window.self.location;
setTimeout(function(){document.body.innerHTML=""},1);
window.self.onload=function(){document.body.innerHTML=""}};

Is this making sure the page isn't rendering inside of a iframe?

if(window.top!==window.self){document.write="";
window.top.location=window.self.location;
setTimeout(function(){document.body.innerHTML=""},1);
window.self.onload=function(){document.body.innerHTML=""}};

Is this making sure the page isn't rendering inside of a iframe?

• javascript
• jquery

Share Improve this question Follow edited Feb 1, 2011 at 14:57 Sachin Shanbhag 55.5k1111 gold badges9191 silver badges103103 bronze badges asked Feb 1, 2011 at 14:53 BlankmanBlankman 267k330330 gold badges795795 silver badges1.2k1.2k bronze badges

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4 Answers 4

Sorted by: Reset to default 5

Yes it would seem that this script attempts makes itself the parent frame if it isn't already. AS Pointy has said, these don't always work. Javascript cannot "break out" of it's owner document in most browsers unless it created that document. Or if the page containing the Javascript was loaded dynamically in such a way that the Same Domain policy isn't in effect. (Likely not the case if your site is in an iframe/frame) In the case of a page that is being opened inside another, the script should not have access to modify the parent document.

Here's the code you posted broken out onto several lines with ments.

if(window.top!==window.self){ // is the outermost document not this document?
  document.write=""; // write an empty text node to the document. (not sure why)
  window.top.location=window.self.location; // set the parent document's location to this document's location.
  setTimeout( function(){document.body.innerHTML=""}, 1); // after 1 millisecond make this document's HTML empty. (Probably a memory leak fix)
  window.self.onload = function(){document.body.innerHTML=""} // Another memory leak fix to clear the current document when it is done loading.
};

It looks like a "frame buster" routine. Whether such things work seems to be a controversial topic.

window.top stands for the topmost window in your browser. In Simple words, its the browser window itself.

The code seems to be clearing all the iframes with blank.

Is this making sure the page isn't rendering inside of a iframe?

An iframe or a frame, yeah. It's trying to break out.

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