The height read-only property of the SVGSVGElement interface describes the vertical size of element as an SVGAnimatedLength. It reflects the <svg> element's height attribute, which may not be the SVG's rendered height.
The CSS height property takes precedence over the <svg> element's height attribute, so the value may not reflect the element's appearance. If both the viewBox and height attributes are omitted, the height property reflects that actual height.
const svg = document.querySelector("svg");
const verticalSize = svg.height;
console.dir(verticalSize.baseVal.value); // the `height` value