How to properly set up Express and mongoDB using mongoDB Node.js driver?

I am new to web development in general. I am trying to insert and find documents in a local mongoDB database through GET and POST requests. I am doing this with a Node.js/Express web server. I've managed to get something working, but I'm not sure if I'm doing the right thing.

First, I wrote client.html to send POST requests.

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8">
    <title>Client</title>
  </head>
  <body>
    <p>Insert something into the database:</p>
    <form action="/items" method="POST">
      <input type="text" name="item">
      <button type="submit">Submit</button>
    </form>
  </body>
</html>

After reading the mongoDB documentation for Node.js, I decided to write my Node.js server as follows, putting all my routes under one connection (approach 1):

const express = require("express");
const app = express();
const port = 5000;

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url, { useUnifiedTopology: true });

app.use(express.urlencoded({ extended: true }));

client.connect(function(err) {
  assert.equal(null, err);
  console.log("Connected successfully to server");
  const db = client.db("my_db");
  const itemsCollection = db.collection("items");

  app.get("/", function(req, res) {
    res.sendFile(__dirname + "/client.html");
  });

  // GET request - find documents
  app.get("/items", function(req, res) {
    itemsCollection.find().toArray(function(err, docs) {
      assert.equal(null, err);
      console.log(docs);
    });
  });

  // POST request - insert document
  app.post("/items", function(req, res) {
    itemsCollection.insertOne(req.body, function(err, result) {
      assert.equal(null, err);
      res.redirect("/");
    });
  });

  app.listen(port, function() {
    console.log(`Listening on port: ${port}`);
  });
});

However, I've also seen people create a new connection for every route, which would be something like this (approach 2):

const express = require("express");
const app = express();
const port = 5000;

const MongoClient = require('mongodb').MongoClient;
const assert = require('assert');
const url = 'mongodb://localhost:27017';
const client = new MongoClient(url, { useUnifiedTopology: true });

app.use(express.urlencoded({ extended: true }));

app.get("/", function(req, res) {
  res.sendFile(__dirname + "/client.html");
});

// GET request - find documents
app.get("/items", function(req, res) {
  client.connect(function(err) {
    assert.equal(null, err);
    console.log("Connected successfully to server");

    const db = client.db("my_db");
    const itemsCollection = db.collection("items");

    itemsCollection.find().toArray(function(err, docs) {
      assert.equal(null, err);
      console.log(docs);
    });
  });
});

// POST request - insert document
app.post("/items", function(req, res) {
  client.connect(function(err) {
    assert.equal(null, err);

    const db = client.db("my_db");
    const itemsCollection = db.collection("items");

    itemsCollection.insertOne(req.body, function(err, result) {
      assert.equal(null, err);
      res.redirect("/");
    });
  });
});

app.listen(port, function() {
  console.log(`Listening on port: ${port}`);
});

Both approaches successfully complete the database operations. I would like to know:

1. Which of these approaches (if any) are recommended, and why?
2. Should I be calling client.close() anywhere in my server code?

Any help is appreciated, thanks!