AWS Cognito PreTokenGeneration handler lambda function - what are the typescript types for (event, context, callback) - Amazon Web Sevices

NullPointer
February 13, 2023
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0 votes
2 Answers

The documentation for the AWS Cognito Pre Token Generation function has node example code, but no typescript example code.

Are there typescript types I can import to strongly type the three parameters passed to the handler function?

import { TypeA, TypeB, TypeC } from '???'; // Are these defined by AWS somewhere?
exports.handler = (event: TypeA, context: TypeB, callback: TypeC) => {
  event.response = {
    // the good stuff goes here
  }
  callback(null, event)
}

Answers

- IdoZamir
- February 13, 2023 at 8:44 am
- 0 votes
0
Try this:
```
import { Callback, Context, PreTokenGenerationTriggerEvent } from "aws-lambda";

exports.handler = (event: PreTokenGenerationTriggerEvent, context: Context, callback: Callback) => {
  event.response = {
    // the good stuff goes here
  }
  callback(null, event)
}
```
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- KevinHakanson
- February 14, 2023 at 4:22 am
- 0 votes
0
@types/aws-lambda contains type definitions for AWS Lambda. Specifically, events of type PreTokenGenerationTriggerEvent from pre-token-generation.d.ts

Also, you can use an async function instead of a callback.
```
import { Context, PreTokenGenerationTriggerEvent } from "aws-lambda";

export const handler = async (
  event: PreTokenGenerationTriggerEvent,
  context: Context
): Promise<PreTokenGenerationTriggerEvent> => {
  console.log(`Event: ${JSON.stringify(event, null, 2)}`);

  // good stuff goes here, like
  event.response.claimsOverrideDetails = {
    claimsToAddOrOverride: {
      'custom:claim': 'custom value'
    }
  };
  return event;
};
```
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