The width read-only property of the SVGFETileElement interface describes the horizontal size of an SVG filter primitive as an SVGAnimatedLength.
It reflects the width attribute of the <feTile> element, which fills a target rectangle with a repeated, tiled pattern of an input image. The attribute is a <length> or a <percentage> relative to the width of the filter region. The default value is 100%. The property value is a length in user coordinate system units.
const feTile = document.querySelector("feTile");
const horizontalSize = feTile.width;
console.log(horizontalSize.baseVal.value); // the `width` value