iswindow

Checks whether value is a window object.

Support

IE8+ is the target. But making it work in IE8 also makes it work in IE6+, so this basically works everywhere, even old Safaris.

Installation

component install darsain/iswindow

Example

var isWindow = require('iswindow');

isWindow(window);       // true
isWindow(anythingElse); // false

Not bulletproof

Uses duck typing and double equals when comparing window objects, which is necessary for this to work in IE8.

Double equals are necessary because in IE8:

window.window === window;                // false
window.document.parentWindow === window; // false
window.window == window;                 // true
window.document.parentWindow == window;  // true
window === window;                       // true
window == window;                        // true

If someone knows why this is happening in IE8, or has a better or more robust method to test for window in IE8+, please let me know in issues.

Hell, we can't even do typeof window.setTimeout === 'function', because in IE8 global functions are 'object'.

That being said, you'd need this to cause a false positive:

var notWin = {};
notWin.window = notWin;
notWin.setTimeout = 'truthy';
notWin.alert = 'truthy';
notWin.document = {};
notWin.document.defaultView = notWin;

isWindow(notWin); // true

License

MIT