A node.js function `watchFile(filePath, contentCallback)` that can handle path like `folder/file.ext` and is ready to folder and/or file not be there at any given point in time.

watch-file.js

const { existsSync, watch, readFile } = require('fs');
const { dirname, basename } = require('path');

function watchFile(filePath, contentCallback) {
  const folderPath = dirname(filePath);
  const folderName = basename(folderPath);
  const parentPath = dirname(folderPath);
  const fileName = basename(filePath);

  let folderExists = existsSync(folderPath);
  let folderWatcher, fileWatcher;

  function watchFolder() {
    folderWatcher = watch(parentPath, (_, name) => {
      if (name !== folderName) return;

      if (existsSync(folderPath)) {
        if (!folderExists) {
          folderExists = true;
          watchFileInFolder();
        }
      } else {
        fileWatcher?.close();
        fileWatcher = null;
        folderExists = false;

        if (!folderWatcher) watchFolder();
      }
    });

    folderWatcher.on('error', (err) => {
      if (err.code === 'EPERM') {
        folderWatcher?.close();
        folderWatcher = null;
      }
    });
  }

  function watchFileInFolder() {
    fileWatcher = watch(folderPath, (_, name) => {
      if (name != fileName) return;

      readFile(filePath, 'utf8', (err, data) => {
        contentCallback(err ? null : data);
      });
    });

    fileWatcher.on('error', (err) => {
      if (err.code === 'EPERM') {
        fileWatcher?.close();
        fileWatcher = null;

        if (!folderWatcher) watchFolder();
      }
    });
  }

  folderExists ? watchFileInFolder() : watchFolder();
}

watchFile('a/d.e', console.log);

It is not ready for deeper paths.