The result read-only property of the SVGFEDropShadowElement interface describes the assigned name of an SVG filter primitive as a SVGAnimatedString.
It reflects the result attribute. The attribute value is a <custom-ident>. If supplied, then graphics that result from processing this filter primitive can be referenced by an in attribute on a subsequent filter primitive within the same <filter> element.
If no result attribute is defined, the filter's result.baseVal and result.animVal are empty strings, and the output of the <feDropShadow> filter will only be available for re-use as the implicit input into the next filter primitive if that filter primitive provides no value for its in attribute.
const feDropShadowElement = document.querySelector("feDropShadow");
const filterName = feDropShadowElement.result;
console.log(filterName.baseVal); // the filter's assigned nameSVGFEDropShadowElement.in1<custom-ident> data typedrop-shadow() functionbox-shadow propertytext-shadow property<blend-mode> data typemix-blend-mode property