deno_hello_world_oak_exp.ts

import { Application } from "https://deno.land/x/oak/mod.ts";

const app = new Application();
app.use(ctx => {
    ctx.response.body = { body: "Hello World" };
});

await app.listen({port: 3000});

node_hello_world_oak_exp.js

const express = require('express');
const app = express();

app.get('/', (req, res) => res.json({body: 'Hello World'}));
app.listen(3000);