Use res.json() and accept URL parameters by using req.params object. More: https://kananrahimov.com/post/example-backend-api-in-node-js-video-tutorial/

server.js

const express = require('express');

const app = express();

//const hostname = '127.0.0.1';
const port = 3000;

app.get('/', (req, res) => {
  let body = {
    "message": "Hello, world!",
    "items": [
      "str1",
      "str2",
      "str3",
      "Hello, world in item 4"
    ]
  };
  const { headers, method, query, url } = req;
  const responseBody = { headers, method, query, url, body };

  res.json(responseBody);
})

app.get('/echo/:name/', (req, res) => {
  const { name } = req.params;
  let body = {
    "message": `Hello, ${name}!`,
    "items": [
      "str1",
      "str2",
      "str3"
    ]
  };

  res.json(body);
})

app.listen(port, () => {
  console.log(`Example app running at ${port} port`);
})