Limiting mouse scroll in viewbox

Question

I have the below code for zooming in and out of a svg viewbox. Is there any way to modify this to limit the zoom out to the view size that is initially loaded on the page?

window.addEventListener("DOMContentLoaded", (event) => {
const svg = document.querySelector('svg');

// zooming
svg.onwheel = function (event) {
    event.preventDefault();

    // set the scaling factor (and make sure it's at least 10%)
    let scale = event.deltaY / 1000;
    scale = Math.abs(scale) < .1 ? .1 * event.deltaY / Math.abs(event.deltaY) : scale;

    // get point in SVG space
    let pt = new DOMPoint(event.clientX, event.clientY);
    pt = pt.matrixTransform(svg.getScreenCTM().inverse());

    // get viewbox transform
    let [x, y, width, height] = svg.getAttribute('viewBox').split(' ').map(Number);

    // get pt.x as a proportion of width and pt.y as proportion of height
    let [xPropW, yPropH] = [(pt.x - x) / width, (pt.y - y) / height];
    
    // calc new width and height, new x2, y2 (using proportions and new width and height)
    let [width2, height2] = [width + width * scale, height + height * scale];
    let x2 = pt.x - xPropW * width2;
    let y2 = pt.y - yPropH * height2;        

    svg.setAttribute('viewBox', `${x2} ${y2} ${width2} ${height2}`);
}

})