I think need to add a little bit more configuration to node.js file, especifically you must add the body-parser dependency so you can extract the entire body portion from the incoming request.
You must install body-parser with npm:
npm install body-parser --save
After that you should add it to your file and add configuration:
const bodyParser = require('body-parser')
const express = require('express');
const app = express();
app.use(bodyParser.json())
app.use(bodyParser.urlencoded({extended: false}))
More information on this post: https://stackoverflow.com/questions/38306569/what-does-body-parser-do-with-express#:~:text=body%2Dparser%20extract%20the%20entire,submitted%20using%20HTTP%20POST%20request.
CLICK HERE to find out more related problems solutions.