html

<svg id="outerSvg" xmlns="http://www.w3.org/2000/svg">
  <g id="group1">
    <circle id="circle1" cx="50" cy="50" r="40" fill="blue" />
  </g>
</svg>

js

const circle = document.getElementById("circle1");
const ownerSVG = circle.ownerSVGElement;

if (ownerSVG) {
  console.log(`The circle's owner <svg> has the ID: ${ownerSVG.id}`);
} else {
  console.log("This element is the outermost <svg>.");
}