How to Position a Popup Window Precisely in the Center of the Screen

Centering a popup window created using JavaScript's window.open function on the screen is essential for optimal user experience. The exact coordinates depend on the screen resolution, so a dynamic solution is required.

Solution: Utilize a Single/Dual Monitor Function

A robust solution that accommodates both single and dual monitor setups is given below:

const popupCenter = ({ url, title, w, h }) => {
    // Determine the positions based on screen resolution
    const dualScreenLeft = window.screenLeft || window.screenX;
    const dualScreenTop = window.screenTop || window.screenY;

    const width = window.innerWidth || document.documentElement.clientWidth || screen.width;
    const height = window.innerHeight || document.documentElement.clientHeight || screen.height;

    // Adjust for system zoom
    const systemZoom = width / window.screen.availWidth;

    // Calculate the centered coordinates
    const left = (width - w) / 2 / systemZoom   dualScreenLeft;
    const top = (height - h) / 2 / systemZoom   dualScreenTop;

    // Open the popup window with the calculated dimensions and positioning
    const newWindow = window.open(url, title,
        `
        scrollbars=yes,
        width=${w / systemZoom},
        height=${h / systemZoom},
        top=${top},
        left=${left}
        `
    );

    if (window.focus) newWindow.focus();
};

Usage Example:

popupCenter({ url: 'http://www.xtf.dk', title: 'xtf', w: 900, h: 500 }); 

Credits and Source:

This solution, originally from http://www.xtf.dk/2011/08/center-new-popup-window-even-on.html, effectively handles popup window centering for a variety of screen configurations.