Function copyProperties

src/polyfills/custom-elements.js:849–869

(obj, prototype)

 * @visibleForTesting
 */
export function copyProperties(obj, prototype) {
  let current = prototype;
  while (current !== null) {
    if (Object.isPrototypeOf.call(current, obj)) {
      break;
    }

    for (const prop of Object.getOwnPropertyNames(current)) {
      if (Object.hasOwnProperty.call(obj, prop)) {
        continue;
      }

      const desc = /** @type {!ObjectPropertyDescriptor<Object>} */ (
        Object.getOwnPropertyDescriptor(current, prop)
      );
      Object.defineProperty(obj, prop, desc);
    }

    current = Object.getPrototypeOf(current);
  }
}

/**
 * Polyfills Custom Elements v1 API. This has 5 modes: