Function isMessagePort

public/lib/pdfjs/pdf.worker.mjs:61634–61636

(maybePort)

  }
}
function isMessagePort(maybePort) {
  return typeof maybePort.postMessage === "function" && "onmessage" in maybePort;
}
if (typeof window === "undefined" && !isNodeJS && typeof self !== "undefined" && isMessagePort(self)) {
  WorkerMessageHandler.initializeFromPort(self);
}