The specularExponent read-only property of the SVGFESpotLightElement interface reflects the specularExponent attribute of the given <feSpotLight> element.
An SVGAnimatedNumber object.
specularExponent attribute of the <feSpotLight> elementIn this example, we access the exponent value controlling the focus of the <feSpotLight> filter element's light source by using the specularExponent read-only property of the SVGFESpotLightElement interface.
<svg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
<defs>
<filter id="specularLightingFilter">
<!-- Apply a specular light effect to the SourceGraphic -->
<feSpecularLighting
in="SourceGraphic"
specularExponent="40"
lighting-color="hotpink"
surfaceScale="5">
<feSpotLight
x="100"
y="100"
z="50"
pointsAtX="100"
pointsAtY="100"
specularExponent="40" />
</feSpecularLighting>
</filter>
</defs>
<circle
cx="100"
cy="100"
r="50"
fill="lightblue"
filter="url(#specularLightingFilter)" />
</svg>// Select the feSpotLight element
const spotLightElement = document.querySelector("feSpotLight");
// Access the specularExponent property
console.log(spotLightElement.specularExponent.baseVal); // Output: 40