Trying to send data from Reactjs Component to express app using axios

Question

I'm working on a project that uses ReactJS typescript for the front-end, express for the back-end, and MongoDB for the database. The main issue I am having is that I want to somehow send data from my React component to the express app so that it can query and add things to the database. Currently, I have the express server running on http://localhost:9000, and the React app on http://localhost:3000, and I can connect them using routes.

My express app looks like the following:

var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');
var cors = require('cors');
var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
var testAPIRouter = require('./routes/testAPI');
var testAddUser = require('./routes/addUser');
const MongoClient = require('mongodb').MongoClient;
const mongoose = require('mongoose');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

app.use(cors());
app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));


app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use("/testAPI", testAPIRouter);
app.use("/addUser", testAddUser);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});


const dbRoute = 'mongodb+srv://Adminname:fjfeinjd@pawornaw-b4vzg.gcp.mongodb.net/test?retryWrites=true&w=majority';
mongoose.connect(dbRoute,
    {useNewUrlParser: true})
    .then(() => console.log("Connected to MongoDB"))
    .catch(err => console.error("Could not connected to Mongo"));

module.exports = app;

and my React Component is this, minus import statements. The render function only contains a button that has an onlclick that executes doThing()

    constructor(props: any) {
        super(props);
        this.state = {
            showHomePage: true,
            showAnimalUploadSearch: false,
            showProfile: false,
            showAnimal: true,
            apiResponse: "",
            fName: "bob"
        };
        this.changeView = this.changeView.bind(this);
        // this.callAPI = this.callAPI.bind(this);
        // this.componentWillMount = this.componentWillMount.bind(this);
        this.doThing = this.doThing.bind(this);
    }

    callAPI() {
        fetch("http://localhost:9000/testAPI")
            .then(res => res.text())
            .then(res => this.setState({apiResponse: res}))
            .catch(err => err);

    }

    componentWillMount(): void {
        this.callAPI();
    }

    changeView() {
        this.setState({showHomePage: !this.state.showHomePage});
        this.setState({showAnimalUploadSearch: !this.state.showAnimalUploadSearch});
        this.setState({showAnimal: true});
        this.setState({showProfile: false});
    }

    doThing() {

        Axios.post('http://localhost:9000/testAPI', ({firstName: this.state.fName}))
            .then(res => console.log(res));

    }

and finally, testAPI.js looks like this

const router = express.Router();
const axios = require('axios');

router.get('/', function(req, res, next) {
//res.send('API is working properly');
    axios.get('http://localhost:3000')
        .then(res => console.log("got it"))
        .catch(err => err);
});

module.exports = router;

I want to be able to access and use the data that is sent from my react component so that I can query my database with user input in the future. The API does connect with my React code, and when the testAPI function only contains these lines:

const router = express.Router();
const axios = require('axios');

router.get('/', function(req, res, next) {
res.send('API is working properly');
});

module.exports = router;

the message can be displayed on my react app in the browser via the state.

If anyone could help me see what I am doing wrong, or maybe give me a clue as to what other options I can try, please let me know.

Thank you.

Answer 1

When you send post request from client side, it will be in body property of req object

const router = express.Router();
 // you shoud listen post request
router.post('/', function(req, res) {
  const { body } = req;
  // do somethin with data which you recieved in body, save to database for example
  // and send response to the client
  res.json({ message: 'your data was saved'});
});

module.exports = router;

to send data to client use:

router.get('/', function(req, res) {
  res.json({ data: 'Some data'}); // or res.send('some text') to send plain text
});