Finally, we are going to create an API that allows a user to delete a given note.

Add the Function

Create a new file delete.js and paste the following code

import * as dynamoDbLib from "./libs/dynamodb-lib";
import { success, failure } from "./libs/response-lib";

export async function main(event, context, callback) {
  const params = {
    TableName: "notes",
    // 'Key' defines the partition key and sort key of the item to be removed
    // - 'userId': Identity Pool identity id of the authenticated user
    // - 'noteId': path parameter
    Key: {
      userId: event.requestContext.identity.cognitoIdentityId,
      noteId: event.pathParameters.id
    }
  };

  try {
    const result = await dynamoDbLib.call("delete", params);
    callback(null, success({ status: true }));
  } catch (e) {
    callback(null, failure({ status: false }));
  }
}

This makes a DynamoDB delete call with the userId & noteId key to delete the note.

Configure the API Endpoint

Open the serverless.yml file and append the following to it.

  delete:
    # Defines an HTTP API endpoint that calls the main function in delete.js
    # - path: url path is /notes/{id}
    # - method: DELETE request
    handler: delete.main
    events:
      - http:
          path: notes/{id}
          method: delete
          cors: true
          authorizer: aws_iam

This adds a DELETE request handler to the /notes/{id} endpoint.

Test

Create a mocks/delete-event.json file and add the following.

Just like before we’ll use the noteId of our note in place of the id in the pathParameters block.

{
  "pathParameters": {
    "id": "578eb840-f70f-11e6-9d1a-1359b3b22944"
  },
  "requestContext": {
    "identity": {
      "cognitoIdentityId": "USER-SUB-1234"
    }
  }
}

Invoke our newly created function from the root directory.

$ serverless invoke local --function delete --path mocks/delete-event.json

And the response should look similar to this.

{
  statusCode: 200,
  headers: {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Credentials': true
  },
  body: '{"status":true}'
}

Now that our APIs are complete; we’ll deploy them next.