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isWindow
function(
a, // input
b // placeholder for property document of a
){
return
// cannot be falsy value, mainly to prevent null and undefined (regarded as global object in some browsers)
!!a &&
// checking types with Object.prototype.toString.call is always a good way
// however, for window, is a bit difficult
// let's see the results in different browsers (except IE678, which return "[object Object]")
// "[object Window]"
// "[object DOMWindow]"
// "[object global]"
// so, we can simply check if the input's [[Class]] is ended with w] or l]
/[wl]]/.test({}.toString.call(a)) ||
// believe me, IE is not a good guy
// why?
// because in which, window == document but document != window
// what a wtf feature!
a == (b=a.document) && b != a
}
(function(a,b){return!!a&&/[wl]]/.test({}.toString.call(a))||a==(b=a.document)&&b!=a})
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
Version 2, December 2004
Copyright (C) 2011 YOUR_NAME_HERE <YOUR_URL_HERE>
Everyone is permitted to copy and distribute verbatim or modified
copies of this license document, and changing it is allowed as long
as the name is changed.
DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. You just DO WHAT THE FUCK YOU WANT TO.
{
"name": "isWindow",
"description": "Check if the input is window.",
"keywords": [
"window",
"isWindow",
"DOM",
"jQUery"
]
}
<!DOCTYPE html>
<title>Foo</title>
<div>Expected value: <b>true</b></div>
<div>Actual value: <b id="ret"></b></div>
<script>
// write a small example that shows off the API for your example
// and tests it in one fell swoop.
var myFunction = (function(a,b){return!!a&&/[wl]]/.test({}.toString.call(a))||a==(b=a.document)&&b!=a})
document.getElementById( "ret" ).innerHTML = myFunction(window)
</script>
@nikola

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commented Oct 5, 2011

I'd say it's safe to eliminate the Object {} scope from the toString() call.

@atk

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commented Oct 6, 2011

You can even eliminate the toString call completely, because .test() coerces its first argument into String.

@tsaniel

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Owner Author

commented Oct 7, 2011

Thanks for your ideas, @nikola and @atk!
However,
@nikola: This may lead to error in older IE versions.
@atk: Something like 'w]' will pass the test.

@atk

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commented Oct 7, 2011

You could try a&&a.alert additionally

@tsaniel

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commented Oct 7, 2011

@atk: Thanks again! But an fake object {alert:1,toString:function(){return 'w]'}} still passes the test.

@atk

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commented Oct 7, 2011

That's true. How about (a||0).constructor===this.Window? Works in all modern browsers (not in IE 7 or older).

@nikola

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commented Oct 7, 2011

Not in Chrome 14.

this.constructor !== window
@atk

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commented Oct 7, 2011

Damn, there it's DOMWindow... /Wi/.test(a.constructor), maybe?

@tsaniel

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commented Oct 7, 2011

{constructor:'Wi'}

@atk

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commented Oct 9, 2011

Let's try this:

function(a,b){b=this.Window||this.DOMWindow;return!!a&&b?a instanceof b:a==(b=a.document)&&b!=a}

@tsaniel

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commented Oct 10, 2011

It is sad that it won't work with iframes...

@atk

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commented Oct 10, 2011

Rewritten to probably work with (i)frames:

function(a,b){return!!a&&(b=a.Window||a.DOMWindow)?a instanceof b:a==(b=a.document)&&b!=a}

@tsaniel

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commented Oct 10, 2011

It cannot work with my chromium 12...

@atk

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commented Oct 10, 2011

Alas, it's not exposed in Chrome. OK, let's try this:

function(a,b){return!!a&&(b=top.constructor)?a instanceof b:a==(b=a.document)&&b!=a}

@tsaniel

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commented Oct 11, 2011

It won't work with (i)frame as well, because the scope of top differs from (i)frame.

@atk

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commented Oct 11, 2011

Right. Any idea how to get DOMWindow in Chrome if its not exposed?

@tsaniel

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commented Oct 11, 2011

The magic __proto__?

@atk

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commented Oct 11, 2011

Doesn't help very much, because it is different between frames.

@tsaniel

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commented Oct 11, 2011

I think it is hard. In fact, the original code is enough.

@phoetry

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commented Dec 2, 2011

Try this:

function(a,b){return a&&a==a[b='window']&&a==a[b][b]}
@nikola

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commented Dec 2, 2011

Clever. Exploiting the fact that any global object is exposed as a property of window, and window itself is a global object.

@tsaniel

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commented Dec 3, 2011

@phoetry: It's clever but it won't work.

var a = {};
a.window = a;
(function(a,b){return a&&a==a[b='window']&&a==a[b][b]})(a) // true
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