Promise

async function externalServiceCall(filename) {
  return new Promise((resolve, reject) => {
    const isError = false;

    if (isError) {
      reject(Error("Error occured from externalServiceCall"));
    } else {
      resolve(filename);
    }
  });
}

async function promiseFn3() {
  throw Error("Error Occured from promiseFn3");
}

async function promiseFn2(filename) {
  const isError = false;
  // complex code logic
  if (isError) {
    return Promise.reject(Error("Error Occured from promiseFn2"));
  } else {
    return Promise.resolve(filename);
  }
}

async function promiseFn(filename) {
  const isError = false;
  // complex code logic
  if (isError) {
    return Promise.reject(Error("Error Occured from promiseFn"));
  } else {
    return Promise.resolve(filename);
  }
}

Function calls :

// Promise function reference print
console.log("promiseFn3 : ", promiseFn3);

promiseFn(FILE_NAME)
  .then((data) => {
    console.log("Data 1 (promiseFn) : ", data);
    return externalServiceCall(FILE_NAME + ".txt");
  })
  .then((data) => {
    console.log("Data 2 (promiseFn) : ", data);
  })
  .catch((error) => {
    console.log("Error (promiseFn) : ", error);
  });