DefinitelyTyped/types/http-proxy/http-proxy-tests.ts

import * as http from "http";
import * as HttpProxy from "http-proxy";

const proxy = new HttpProxy({
  changeOrigin: true
});

proxy.on("error", (err) => {
  console.error("An error occured:", err);
});

/**
 * Test type inference of event listener parameters:
 */
proxy.on("start", (req, res, target) => {
  const headers = req.headers; // defined;
  const status = res.statusCode; // defined;
  const partial =
    typeof target === "string"
      ? target.substr(0) // defined;
      : target.protocol; // defined;
});

http.createServer((req, res) => {
  proxy.web(req, res);
});