The y read-only property of the SVGFEConvolveMatrixElement interface describes the vertical coordinate of the position of an SVG filter primitive as a SVGAnimatedLength.
It reflects the <feConvolveMatrix> element's y filter primitive attribute value. The <feConvolveMatrix> filter applies a matrix convolution effect, combining pixels in the input image with neighboring pixels to produce a convolution effect such as blurring, edge detection, sharpening, embossing or beveling.
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 feConvolveMatrix = document.querySelector("feConvolveMatrix");
const topPosition = feConvolveMatrix.y;
console.log(topPosition.baseVal.value); // the `y` valueSVGFEConvolveMatrixElement.x<filter> element, SVG filter attribute in SVG