The y read-only property of the SVGFEDiffuseLightingElement interface describes the vertical coordinate of the position of an SVG filter primitive as a SVGAnimatedLength.
It reflects the <feDiffuseLighting> element's y filter primitive attribute value. The filter lights an image using the alpha channel as a bump map. The attribute is a <length> or <percentage>. The <coordinate> is a length in the user coordinate system that is the given distance from the origin of the filter along the y-axis. If the y attribute is a percent value, the property value is a relative to the height of the filter region in user coordinate system units. The default value is 0.
const feDiffuseLighting = document.querySelector("feDiffuseLighting");
const topPosition = feDiffuseLighting.y;
console.log(topPosition.baseVal.value); // the `y` valueSVGFEDiffuseLightingElement.xSVGFESpecularLightingElement<feSpecularLighting><blend-mode> data typemix-blend-mode property