how to make api calls in nodejs code example

Example: wwhat is rest api calls in node js

const userRoutes = (app, fs) => {
  //...unchanged ^^^

  // refactored helper methods
  const readFile = (
    callback,
    returnJson = false,
    filePath = dataPath,
    encoding = 'utf8'
  ) => {
    fs.readFile(filePath, encoding, (err, data) => {
      if (err) {
        throw err;
      }

      callback(returnJson ? JSON.parse(data) : data);
    });
  };

  const writeFile = (
    fileData,
    callback,
    filePath = dataPath,
    encoding = 'utf8'
  ) => {
    fs.writeFile(filePath, fileData, encoding, err => {
      if (err) {
        throw err;
      }

      callback();
    });
  };

  // READ
  // Notice how we can make this 'read' operation much more simple now.
  app.get('/users', (req, res) => {
    readFile(data => {
      res.send(data);
    }, true);
  });
};

module.exports = userRoutes;