Use closed to determine whether a window that you opened, and to which you still hold a reference (from the return value of window.open), is still open. Once a window is closed, you should not attempt to manipulate it. Since window.closed is only supported by Internet Explorer 4, and Navigator 3, and later, you should account for previous versions. We'll use the following code:

// if win and win.open exist, and win.closed is not true, move the window
if (win && win.open && !win.closed) win.moveTo(0, 0);

Internet Explorer 3 and Navigator 2 don't support the closed property, so it evaluates to false in a Boolean expression (like any property that doesn't exist, such as window.tomershiran).

Learn more about windows in Tutorial 1.

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