如何修复Restful API和ReactJS上的204网络代码（无内容）？

Question

我尝试在node.js和react上用restful api创建非常简单的联系表单，但是当我尝试发送消息时，我收到了网络代码200，而后我收到了网络代码204，没有内容。

有什么办法可以解决这个问题，因为我的邮件没有发过来。

我的Api.js文件看起来是这样的。

const express = require('express');
const bodyParser = require('body-parser');
const nodemailer = require('nodemailer');
const cors = require('cors');

const app = express();

const port = 4000;

app.use(cors());

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

app.get('/', (req, res) => {
  res.send('Welcome to my api');
})

app.post('/api/v1/', (req,res) => {
  const { body: { username, password }} = req;
  const params = req.params;
  console.log(params)
  var data = req.body;

var smtpTransport = nodemailer.createTransport({
  service: 'Gmail',
  port: 465,
  auth: {
    user: '[email protected]',
    pass: 'somepassword'
  }
});

var mailOptions = {
  from: data.email,
  to: '[email protected]',
  subject: 'New Request',
  html: `<p>${data.name}</p>
          <p>${data.email}</p>
          <p>${data.message}</p>`
};

smtpTransport.sendMail(mailOptions,
(error, response) => {
  if(error) {
    res.send(error)
  }else {
    res.send('Success')
  }
  smtpTransport.close();
});

})

app.listen(port, () => {
  console.log('We are live on port 4000');
});

我的App. js文件是这样的

import React, { Component } from 'react';
import axios from 'axios';


class Contact extends Component {

    state = {
        name: '',
        message: '',
        email: '',
        username: '',
        password: '',
        sent: false,
        buttonText: 'Send Message'
    }

    formSubmit = (e) => {
        e.preventDefault()

        this.setState({
            buttonText: '...sending'
        })

        let data = {
            name: this.state.name,
            email: this.state.email,
            message: this.state.message,
            username: this.state.username,
            password: this.state.password
        }

        axios.post("http://wwww.localhost:4000/api/v1/", data)
        .then( res => {
            this.setState({ sent: true }, this.resetForm())
        })
        .catch( () => {
          console.log('Message not sent')
        })
      }

      resetForm = () => {
        this.setState({
            name: '',
            message: '',
            email: '',
            buttonText: 'Message Sent'
        })
    }

    render() {
        return(
          <form className="contact-form" onSubmit={ (e) => this.formSubmit(e)}>
          <label className="message" htmlFor="message-input">Your Message</label>
          <br/>
          <textarea onChange={e => this.setState({ message: e.target.value})} name="message" className="message-input" type="text" placeholder="Please write your message here" value={this.state.message} required/>
          <br/>
          <label className="message-name" htmlFor="message-name">Your Name</label>
          <br/>
          <input onChange={e => this.setState({ name: e.target.value})} name="name" className="message-name" type="text" placeholder="Your Name" value={this.state.name}/>
          <br/>
          <label className="message-email" htmlFor="message-email">Your Email</label>
          <br/>
          <input onChange={(e) => this.setState({ email: e.target.value})} name="email" className="message-email" type="email" placeholder="[email protected]" required value={this.state.email} />

          <div className="button--container">
              <button type="submit" className="button button-primary">{ this.state.buttonText }</button>
          </div>
        </form>
        );
    }
}

export default Contact;

奇怪的是两个星期前我没有收到204这样的网络错误 我只收到了网络代码200 ОК和邮件。

我可以举例说明如何解决这个错误吗？