The height read-only property of the SVGFEOffsetElement interface describes the vertical size of an SVG filter primitive as an SVGAnimatedLength.
It reflects the height attribute of the <feOffset> element, which offsets the input image relative to its current position. The attribute is a <length> or a <percentage> relative to the height of the filter region. The default value is 100%. The property value is a length in user coordinate system units.
const feOffset = document.querySelector("feOffset");
const verticalSize = feOffset.height;
console.log(verticalSize.baseVal.value); // the `height` value