Check if it's the window object
javascript
Solution
This will not only test for current window, but for window in general:
if (window.toString() === "[object Window]") {
// your code here
}
[edit]
`toString()` object prototype was available from JavaScript initial version 1.0 and was an old fashioned way to check for the "class". As well as the method mentioned in another answer to this question - to check for the unique object propert, which is faster to execute than string comparison.
Since JavaScript 1.4 (ECMAScript 3rd edition 1999) we are able to utilize `instanceof` operator to check for the object Class which is the right method for this task.
if (window instanceof Window) {
// your code here
}
Problem
Given that my plugin could be run on any JS engine (in a browser or not), How does one know that some variable is actually the browser `window` object. Like how do I know if `someVar` references the browser `window` object. Is there something in `window` that I can check if it is really the browser `window` object? And how to check if the browser `window` object actually exists and not just some `window` variable containing an object. Suppose you can't tell if `someVar` is `window` by itself, and you want to match it against the real browser `window` object like `someVar === window`, how do you get `window` that you are sure it is the browser `window` and not some other object from an outer scope named `window`, or some other global from another environment? Just to clarify a bit more: - I'm not looking for the global of the environment. I'm looking for the browser `window` object specifically. - I'm not checking if the script is running on the browser. I can't do something like `if(!window)` since `window` could just be another object declared somewhere outside the scope. ``` function someFunction(){ var window = {foo:'bar'}; (function(){ console.log(window); //{foo:'bar'} }()); } ``` I can't check `if(window.window === window)` since I can also do self referencing, and like said earlier, `window` could be an object from an outer scope: ``` var bar = {}; bar.bar = bar; bar.bar.bar.bar.bar.bar === bar; //true ``` And the following may not work since the script could be wrapped or concatenated within something other than the global space. `this` could also be modified with calls like `call()`, `apply()` or `bind()`. ``` //Stand-alone, I can assume window is global since "this" is the global in global space (function(window){ //window may not be window }(this)); //But when this happens someNamespace.someFunction = function(){ (function(window){ //window may not be window }(this)); } //or this: someNamespace.someFunction.call({}); ``` I have a feeling that this is a duplicate, but I couldn't find where I first saw it.