抛出错误 UnhandledPromiseRejection 后，NodeJS 程序未退出

Question

I have a function written in JavaScript. I'm trying to call a function which performs some work from my main function. I have put a condition in the calling function to look for an employee id and if null then I'm returning the error and would like to exit gracefully from my main function. But this thing is not happening. Program is keep on executing to next code and functions and there getting below error:-

{ "errorType": "Runtime.UnhandledPromiseRejection", "errorMessage": "Error: Employee number is mandatory", "reason": { "errorType": "Error", "errorMessage": "Employee number is mandatory", "stack": [ "Error: Employee number is mandatory", " at /var/task/index.js:64:23", " at Array.forEach ()", " at transformData (/var/task/index.js:58:22)", " at /var/task/index.js:207:43", " at processTicksAndRejections (internal/process/task_queues.js:97:5)", " at async Promise.all (index 0)", " at async Runtime.exports.lambdaHandler [as handler] (/var/task/index.js:258:5)" ] }, "promise": {}, "stack": [ "Runtime.UnhandledPromiseRejection: Error: Employee number is mandatory", " at process. (/var/runtime/index.js:35:15)", " at process.emit (events.js:315:20)", " at process.EventEmitter.emit (domain.js:482:12)", " at processPromiseRejections (internal/process/promises.js:209:33)", " at processTicksAndRejections (internal/process/task_queues.js:98:32)" ] }

Main function code snippet:-

try{
      const data = await transformData(list, mymap, tenantId);
      if (data === null || data === undefined) {
        throw Error(`Error in transforming the data`);
      }
      const syncDataResponse = await syncDetails(tenantId!, data); //Calling is going here
 } catch (err) {
    console.log(err);
}

Calling function:-

const transformData = async (list: any, mymap: Map<string, string>, tenantId: string) => {
  const data = [];
  try {
    await list.forEach(async (obj: { [x: string]: any; employee_number?: any; }) => {
      modifyKeys(obj, mymap);

      if (obj && obj.employee_number) {
        data.push({ employeeId: obj.employee_number, employeeDetails: obj });
      } else {
        throw Error(`Employee number is mandatory`);
      }

    });
  } catch (err) {
    console.log('Error while transforming the data::', err);
    return err;
  }
  return data;
}

I was expecting program exit gracefully when I'm throwing the error in the transformData function when the employee id is null but in my main method, the program does executes the next function called syncDetails() and I'm getting this unhandledpromiserejection error.

Pleas suggest. Cheers

Answer 1

In transformData you are using list.foreach method where your promise is going into the loop and they are continuous throwing error.

Instead of using list.foreach, I suggest use Promise.All

Answer 2

Convert your forEach in transformData to for ... of or a traditional for loop instead.

Although forEach is synchronous in nature, it does NOT recognize async functions.

Refer to these articles for more info -

article 1

article 2