handler.js

'use strict';

const fetch = require('node-fetch');

/**
 * Use this command to launch the handler from console:
 *
 * node_modules/.bin/serverless invoke local -f lambda -d '{"httpMethod":"GET","queryStringParameters":{"url":"http://github.com"}}'
 *
 *  or from browser
 *
 * http://localhost:3000/?url=https://github.com
 */
module.exports.corsProxy = async (event) => {
  return new Promise(async (resolve, reject) => {
    let params = event.queryStringParameters;
    let { Host, host, Origin, origin, ...headers } = event.headers;

    console.log(event);
    console.log(`Got request with params:`, params);

    if (!params.url) {
      const errorResponse = {
        statusCode: 400,
        body: "Unable get url from 'url' query parameter",
      };
      reject(Error(errorResponse));
      return;
    }

    const requestParams = Object.entries(params)
      .reduce((acc, param) => {
        if (param[0] !== 'url') acc.push(param.join('='));
        return acc;
      }, [])
      .join('&');

    const url = `${params.url}${requestParams}`;
    const hasBody = /(POST|PUT)/i.test(event.httpMethod);
    try {
      const res = await fetch(url, {
        method: event.httpMethod,
        timeout: 20000,
        body: hasBody ? event.body : null,
        headers,
      });
      console.log(`Got response from ${url} ---> {statusCode: ${res.status}}`);

      let proxyResponse = {
        statusCode: res.status,
        headers: {
          'Access-Control-Allow-Origin': '*', // Required for CORS support to work
          'Access-Control-Allow-Credentials': true, // Required for cookies, authorization headers with HTTPS
          'content-type': res.headers['content-type'],
        },
      };

      const body = await res.text();
      proxyResponse.body = body;
      resolve(proxyResponse);
    } catch (err) {
      console.error(`Caught error: `, err);

      reject(err);
      return;
    }
  });
};