Finding the centre of a web page

I wanted to quickly find the centre of a page so I could visually confirm for myself that an element was placed smack dab in the middle. Maybe there's better ways to do this, but pasting this little snippet in your browser's console does the trick just fine.

{% raw %}
(function() {
    const style = `
        .center-line {
            position: fixed;
            background: red;
            z-index: 9999;
            pointer-events: none;
        }
        .vertical {
            width: 2px;
            height: 100vh;
            top: 0;
            left: 50%;
            transform: translateX(-50%);
        }
        .horizontal {
            height: 2px;
            width: 100vw;
            left: 0;
            top: 50%;
            transform: translateY(-50%);
        }
    `;

    const styleEl = document.createElement("style");
    styleEl.innerHTML = style;
    document.head.appendChild(styleEl);

    const verticalLine = document.createElement("div");
    verticalLine.classList.add("center-line", "vertical");

    const horizontalLine = document.createElement("div");
    horizontalLine.classList.add("center-line", "horizontal");

    document.body.appendChild(verticalLine);
    document.body.appendChild(horizontalLine);
})();
{% endraw %}