每次调用trackNotifications()时，都会创建一个新的空queuedNotifications数组。您需要将所有代码 Package 在IIFE中以创建闭包，因此queuedNotifications的声明在trackNotifications()函数之外。

((data) => {
  const timeInMsToReleaseNotification = 1000 * 15; // 15 seconds
  let queuedNotifications: Notification[] = [];
  let timeoutId: NodeJS.Timeout | null = null;

  const trackNotifications = (data: Notification) => {
    if (timeoutId) {
      clearTimeout(timeoutId);
    }

    queuedNotifications.push(data);

    timeoutId = setTimeout(() => {
      const foundData = queuedNotifications[0];

      if (foundData) {
        displayNotification(
          foundData,
          queuedNotifications.length > 1 ?
          'nearbyBatch' :
          'nearbySingle',
        );
        queuedNotifications = [];
        timeoutId = null;
      }
    }, timeInMsToReleaseNotification);
  };

  trackNotifications(data);
})(data);

然而，在ES6中，你不需要闭包。用let和const声明的变量是块作用域的，所以你可以简单地把所有代码放在一个块中。

{
  const timeInMsToReleaseNotification = 1000 * 15; // 15 seconds
  let queuedNotifications: Notification[] = [];
  let timeoutId: NodeJS.Timeout | null = null;

  const trackNotifications = (data: Notification) => {
    if (timeoutId) {
      clearTimeout(timeoutId);
    }

    queuedNotifications.push(data);

    timeoutId = setTimeout(() => {
      const foundData = queuedNotifications[0];

      if (foundData) {
        displayNotification(
          foundData,
          queuedNotifications.length > 1 ?
          'nearbyBatch' :
          'nearbySingle',
        );
        queuedNotifications = [];
        timeoutId = null;
      }
    }, timeInMsToReleaseNotification);
  };

  trackNotifications(data);
}

你可以做的一件事是把所有的东西都 Package 在一个IIFE中，这样就限制了变量的作用域，只有trackNotifications可以访问它们。

const trackNotifications = (function () {
  const timeInMsToReleaseNotification = 1000 * 15; // 15 seconds
  let queuedNotifications: Notification[] = [];
  let timeoutId: NodeJS.Timeout | null = null;

  return (data: Notification) => {
    if (timeoutId) {
      clearTimeout(timeoutId);
    }

    queuedNotifications.push(data);

    timeoutId = setTimeout(() => {
      const foundData = queuedNotifications[0];

      if (foundData) {
        displayNotification(
          foundData,
          queuedNotifications.length > 1
            ? 'nearbyBatch'
            : 'nearbySingle',
        );
        queuedNotifications = [];
        timeoutId = null;
      }
    }, timeInMsToReleaseNotification);
  };
})();

// call the function like this
trackNotifications(data);