open popup in center of screen ( popup window javascript )

      
        function openPopUpInCenter() {
            var w1 = 400;
            var h1 = 450;
            var left = (screen.width / 2) - (w1 / 2);
            var top = (screen.height / 2) - (h1 / 2);
            window.open('AddPopup.aspx', 'add', 'top=' + top + ',left=' + left + ',width=' + w1 + ',height=' + h1 + ',location=no, directories=no, status=no, menubar=no, scrollbars=no, resizable=no, copyhistory=no');
        }

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