A Three.js helper function which determines if the given scene contains lights

sceneHasLights.ts

import * as THREE from 'three';

/**
 * Determine if the given scene contains any lights, i.e. objects
 * that are subclasses of the `THREE.Light` abstract base class.
 * 
 * @param scene the scene to check for lights
 * 
 * @returns whether or not the scene contains lights
 */
export function hasLights(scene: THREE.Scene): boolean {
  // Add lights to camera so that the camera can "see" them and render them
  let sceneHasLights = false;

  // The original `traverse()` callback has the signature `(object: THREE.Object3D) => any`.
  // We're modifying it so that we can check to see if `object` is a `THREE.Light` subclass.
  scene.traverse((object: THREE.Object3D | THREE.Light) => {
    if ('isLight' in object) {
      console.log('Found light in scene', object);
      // This line has a TypeScript error in Three.js r103:
      object.isLight; // ERROR: Property 'isLight' does not exist on type 'never'.ts(2339)
      sceneHasLights = true;
    }
  });

  return sceneHasLights;
}