Possible to call a Javascript method in the context of another window?

Question

Say you have a global function alert2:

function alert2(msg) {
    window.alert(msg);
}

And you also have a reference to a second window obj

Answer 1

Note: This only works if both windows belong to the same domain (Single Domain Policy).

What you can do is create function in the childWindow:

var func = function() {
    var parent = window; // pointer to parent window
    var child = childWindow;

    return function() {

        ... anything you like to do ...
        parent.alert('Attached to main window')
        child.alert('Attached to child window')
    }
}();

childWindow.func = func; // pass function to child window

The nested functions make sure that you can access the references from the context where the function was created (note the }(); at the end which terminates the first function and calls it immediately).

The last line creates the new function in the child window; all JavaScript code in the child window can access it as window.func, too.

It's a bit confusing but just think of it like this: You have two window instances/objects. Just like with any JavaScript object, you can assign new properties to them.

Answer 2

You can use childWindow.opener to get the window object that opened the child window.

alert2.call(childWindow.opener, "called from child using parent as context");

Demo: http://jsfiddle.net/hJ7uw/8/