I am in the process of learning about client and server side and sending things back and forth.

I am running an express server and trying to get a log in my console on the server side.

This is my server.js:

//Imports
const express = require('express');

//Setup and configure app
const app = express();
const port = 5000;

//parse JSON files
app.use(express.json());

//serve static files
app.use(express.static('public'));

//Initialize app
app.listen(port, () => console.log(`Server listening on port ${port}!`));

app.post('/api', (request, response) => {
  console.log(request.body);
});

Why does this work and give an output on the console:

const data = {
    name: 'john',
    age: 28
};

const options = {
  method: 'post',
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify(data)
};

fetch('/api', options);

And when I change the variable data to a simple string it does not work:

const data = "hello";

And I will get this parsing error:

SyntaxError: Unexpected token " in JSON at position 0

Same behavior for integers.

Any help is greatly appreciated!