2KB CORS proxy cli util

microCorsProxy.js

/**
* -p proxy listen requests incoming to this port 
* -t proxy request resourse from this target without cors
*
* USAGE EXAMPLE
* node microCorsProxy.js -t http://site-without-cors.com -p 5000
**/

const express = require('express');
const request = require('request');
const bodyParser = require('body-parser');
const app = express();

app.use(bodyParser.json({limit: '1024kb'}));
const filtrateHeaders = objectFilter(['host', 'origin', 'pragma', 'referer']);

function objectFilter(blackList) {
  return obj => Object.entries(obj)
    .reduce((acc, [k,v]) => blackList.includes(k) ? acc : (acc[k] = v, acc), {});
}

function parseArgs(args) {
  const params = { _flags: [] };
  for (let i = 0; i < args.length; i++) {
    args[i][0] === '-'
      ? (params[args[i].slice(1)] = args[i + 1], i++)
      : params._flags.push(args[i]);
  }
  return params;
}

function init(args) {
  const params = parseArgs(args);
  if (params.t === undefined) {
    console.log('\x1b[33m%s\x1b[0m', 'Redirect target for proxy not specified');
    console.log('Use -t <url> for set target');
    return;
  }

  if (params.p === undefined) {
    console.log('\x1b[33m%s\x1b[0m', 'Port not specified');
    console.log('Use -p <url> for set port');
    params.p = process.env.PORT || 4000;
    console.log('Fallback to default port:', params.p);
  }

  const router = (req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*');
    res.header('Access-Control-Allow-Methods', 'GET, PUT, PATCH, POST, DELETE');
    res.header('Access-Control-Allow-Headers', req.header('access-control-request-headers'));
  
    if (req.method === 'OPTIONS') {
      res.send();
    } else {
      console.log('\x1b[32m%s\x1b[0m', `[PROXY] ${req.url} -> ${params.t + req.url}`);
      const popHeaders = ['host', 'origin', 'pragma', 'referer'];
      request(
        {
          url: params.t + req.url,
          method: req.method,
          json: req.body,
          headers: filtrateHeaders(req.headers)
        },
        (error, response, body) =>  {
          console.log(response.statusCode)
          error && console.error('\x1b[31m%s\x1b[0m', 'error: ' , error);
        }
      ).pipe(res);
    }
  };

  app.all('*', router);
  app.set('port', params.p);
  app.listen(app.get('port'), function () {
    console.log('---------------------------------');
    console.log('Proxy server started at port', app.get('port'));
    console.log('---------------------------------');
  });
}

init(process.argv.slice(2));