JSONP-proxy.js

const http = require('http');
const { parse: urlParse } = require('url');
const { parse: querystringParse } = require('querystring');
const log = require('fancy-log');
const chalk = require('chalk');
const env = require('minimist')(process.argv.slice(2));

const getUrlVar = (where, item) => querystringParse(urlParse(where).query)[item];
const line = '-'.repeat(80);

// destructuring & default
const {
  hostname = 'romantycylekkichobyczajow.pl',
  port = 80,
  serverPort = 1337,
  method = 'get',
  requiredUrl = '/wp-json/wp/v2/',
  requiredContentType = 'application/json',
} = env;

log(chalk.yellow(`running localhost:${serverPort}`));
log(chalk.yellow('getting json(p) data'));
log(chalk.yellow(`from ${hostname}:${port}${requiredUrl}...`));
log(chalk.yellow(`visit localhost:${serverPort}${requiredUrl}...`));
log(chalk.gray(line));

function onRequest(clientReq, clientRes) {
  const options = {
    hostname,
    port,
    path: clientReq.url,
    method,
  };

  const proxy = http.request(options, function (res) {
    const contentType = res.headers['content-type'];
    const url = clientReq.url;

    if (!url.includes(requiredUrl) || !contentType.includes(requiredContentType)) {
      res.pipe(clientRes, { end: true });
      log(chalk.gray(`skip  (${res.headers['content-type']}) ${clientReq.url}`));

      return;
    }

    let body = '';
    const callBackName = getUrlVar(clientReq.url, 'callback') || 'autoCallBackNamePassCallbackParam';

    res
      .on('data', chunk => {
        body += chunk;
      })
      .on('end', () => {
        body = callBackName + '(' + body + ');';
        res.headers['content-type'] = 'text/javascript; charset=utf-8';
        res.headers['content-length'] = body.length;
        clientRes.writeHead(res.statusCode, res.headers);
        clientRes.end(body);
      });
    log(`${chalk.blue('serve')} (${chalk.gray(res.headers['content-type'])}) ${clientReq.url}`);
    log(querystringParse(urlParse(clientReq.url).query));
    log(chalk.gray(line));
  });

  clientReq.pipe(proxy, { end: true });
}

http.createServer(onRequest).listen(serverPort);