Reaguj na żądania POST za pomocą Express/Node i MongoDB

użyj body-parser

w swoim kodzie ekspresowym dodaj :

global.bodyParser = require('body-parser');

app.use(bodyParser.urlencoded({
  extended: true,
  limit: '50mb',
  parameterLimit: 100000
}))
app.use(bodyParser.json({
  limit: '50mb',
  parameterLimit: 100000
}))


app.post('/stored', (req, res) => {
    console.log(req.body);
    db.collection('quotes').insertOne(req.body, (err, data) => {
        if(err) return console.log(err);
        res.send(('saved to db: ' + data));
    })
});

w twoim frontendzie :

handleSubmit:function(e){
   e.preventDefault();
    let databody = {
        "name": this.state.nameIn,
        "quote": this.state.quoteIn
    }

    fetch('http://localhost:5002/stored', {
            method: 'POST',
            body: JSON.stringify(databody),
            headers: {
                'Content-Type': 'application/json'
            },
        })
        .then(res => res.json())
        .then(data => console.log(data));
}