• First and foremost, let's set up the AWS SDK and create an instance of the Cognito Identity Service Provider, specifying the AWS region.

» Initialization

const AWS = require('aws-sdk');
const cognitoIdentityServiceProvider = new AWS.CognitoIdentityServiceProvider({ region: 'ap-southeast-1' });

• Use function named handler, which is the entry point for the Lambda function. The function takes an event parameter, which is typically passed when you invoke the Lambda function.

exports.handler = async (event) => {

• Next, use the adminGetUser method to attempt to fetch the user data. Then, check if the email_verified attribute is set to true, indicating that the email has already been verified.

try {
  const userData = await cognitoIdentityServiceProvider.adminGetUser(getUserParams).promise();
  const emailVerified = userData.UserAttributes.find(attr => attr.Name === 'email_verified').Value === 'true';

• Finally, leverage the resendConfirmationCode method to resend the confirmation code to the user's email address.

await cognitoIdentityServiceProvider.resendConfirmationCode(resendParams).promise();
return {
  statusCode: 200,
  body: JSON.stringify('Confirmation code resent successfully'),
};

Here is full code for resending confirmation code in Cognito.

const AWS = require('aws-sdk');
const cognitoIdentityServiceProvider = new AWS.CognitoIdentityServiceProvider({ region: 'ap-southeast-1' });

exports.handler = async (event) => {
  if (event && event.email) {
    const email = event.email;

    const getUserParams = {
      UserPoolId: 'ap-southeast-1_xxxxxx',
      Username: email,
    };

    try {
      const userData = await cognitoIdentityServiceProvider.adminGetUser(getUserParams).promise();
      const emailVerified = userData.UserAttributes.find(attr => attr.Name === 'email_verified').Value === 'true';

      if (emailVerified) {
        return {
          statusCode: 200,
          body: JSON.stringify('Email address is already verified.'),
        };
      } else {
        const resendParams = {
          ClientId: 'xxxxxxxxxxxxxxxxxxx',
          Username: email,
        };

        await cognitoIdentityServiceProvider.resendConfirmationCode(resendParams).promise();

        return {
          statusCode: 200,
          body: JSON.stringify('Confirmation code resent successfully'),
        };
      }
    } catch (error) {
      return {
        statusCode: 500,
        body: JSON.stringify(`Failed to check or resend confirmation code. Furthermore, you can view ${error.message}`),
      };
    }
  } else {
    return {
      statusCode: 400,
      body: JSON.stringify('Missing or invalid email parameter in the request.'),
    };
  }
};

Note: To learn how to grant the necessary permissions to a service role for using the adminGetUser method, you can refer to the following article How to Set Up and Manage IAM Identity Center in AWS