Lambda + API Gateway Response Skelton

handler.js

module.exports.handler = (event, context, callback) => {
  const headers = {
    'Access-Control-Allow-Origin': '*',
    'Access-Control-Allow-Credentials': true
  };
  const invalidResponse = {
    statusCode: 400,
    headers,
    body: JSON.stringify({ error: 'Invalid.' })
  };

  if (false) {
    callback(null, invalidResponse);
    return;
  }

  callback(null, {
    statusCode: 200,
    headers,
    body: JSON.stringify({ message: 'Success' })
  });
};