This is very confusing as seen in #12974 or #12906. My suggestion would be "legacy."
var pdfManager;
    var terminated = false;
    var cancelXHRs = null;
    var WorkerTasks = [];
    const verbosity = getVerbosityLevel();
    const apiVersion = docParams.apiVersion;
    const workerVersion =
      typeof PDFJSDev !== "undefined" && !PDFJSDev.test("TESTING")
        ? PDFJSDev.eval("BUNDLE_VERSION")
        : null;
    if (apiVersion !== workerVersion) {
      throw new Error(
        `The API version "${apiVersion}" does not match ` +
          `the Worker version "${workerVersion}".`
      );
    }
    if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
      
      
      
      
      
      
      const enumerableProperties = [];
      for (const property in []) {
        enumerableProperties.push(property);