SVGFESpecularLightingElement：specularConstant 属性

<svg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg">
  <defs>
    <filter id="specularLightingFilter">
      <!-- Applies specular lighting with a constant specular reflectance -->
      <feSpecularLighting
        in="SourceGraphic"
        specularConstant="0.5"
        lighting-color="hotpink">
        <fePointLight x="50" y="50" z="30" />
      </feSpecularLighting>
    </filter>
  </defs>
  <rect
    x="20"
    y="20"
    width="100"
    height="100"
    fill="lightblue"
    filter="url(#specularLightingFilter)" />
</svg>

// Select the feSpecularLighting element
const specularLightingElement = document.querySelector("feSpecularLighting");

// Access the specularConstant property
console.log(specularLightingElement.specularConstant.baseVal); // Output: 0.5