AWS Proxy Lambda

index.mjs

const TARGET = process.env.TARGET_BASE_URL;

export const EXCLUDED_HEADERS = [
  'accept-encoding',
  'connection',
  'content-encoding',
  'content-length',
  'host',
  'server',
  'transfer-encoding',
  'x-amzn-cipher-suite',
  'x-amzn-tls-version',
  'x-amzn-trace-id',
  'x-amzn-vpc-id',
  'x-amzn-vpce-config',
  'x-amzn-vpce-id',
  'x-apigw-api-id',
  'x-forwarded-for',
  'vary',
];

export const handler = async (event) => {
  const method = event.httpMethod ?? event.requestContext.http.method;
  const path = (event.rawPath ?? event.path);
  const url = new URL(`${TARGET}${path}`);
  
  if(event.queryStringParameters) {
    for(const [key, value] of Object.entries(event.queryStringParameters)) {
        url.searchParams.append(key, value);
    }
  }
  
  const body = event.isBase64Encoded ? Buffer.from(event.body, 'base64') : event.body;
  
  const headers = event.headers;
  
  for (const header of EXCLUDED_HEADERS) {
    delete headers[header];
  }

  const result = await fetch(url, {
    method,
    headers,
    body: method !== 'GET' ? body : undefined,
  });
  
  const responseHeaders = {};
    
  for (const [key, value] of result.headers) {
    if(!EXCLUDED_HEADERS.includes(key.toLowerCase())) {
      responseHeaders[key] = value;
    }
  }
  const response = await result.text();

  return {
    statusCode: result.status,
    headers: responseHeaders,
    body: response,
  };
};