I met the problem that the req.body of my Node.js always got undefined or NULL.

I found many past post. Some mentioned about the need of post-method, the body-parser and the need of property name of the tag. But not working for me at all. All I've added in my code.

server.js

```
const port = "5411";
const express = require('express');
const bodyParser = require('body-parser');
const mysql = require('mysql');
const bcrypt = require('bcrypt');
const app = express()

app.listen(port, function () {
  console.log("server is running on " + port);
});
app.use('/static', express.static("static"));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

const db_con = mysql.createConnection({
  host: "localhost",
  user: "root",
  password: "mitac123",
  database: "human_resource"
});

db_con.connect(function (err) {
  if (err) throw err;
  console.log("DB Connected!");
});

app.get("/upload", function (req, res) {
  res.sendFile(__dirname + "/html/homework.html");
});

app.post("/upload", function (req, res) {
  let name = req.body.name;           //it's here that I use console.log that get NULL or undefined
  let username = req.body.username;
  let password = req.body.password;
  let gender = req.body.gender;
  let email = req.body.email;
  let question = req.body.securityQ;
  let answer = req.body.answer;
  DB_CreateOrUpdate(res, name, username, password, gender, email, question, answer);
})

function DB_CreateOrUpdate(res, name, username, password, gender, email, question, answer){
  saltRounds = 10;
  data = {
    realName: String(name), 
    username: String(username),
    password: bcrypt.hash(password, saltRounds),
    gender: gender,
    email: String(email),
    securityQ: question,
    answer: answer,
  }
  var sql_com = "INSERT INTO user_data SET ?"

  db_con.query(sql_com, data, function (err, result) {
    if (err) throw err;
    console.log("1 record inserted");
    console.log(result);
    return res.send("Add successful!");
  })
};

```

HTML file

```html
<!DOCTYPE html>
<html lang="zh-Hant-TW">

<head>
    <meta charset="utf-8">
    <meta name="author" content="JustBelieveMe">
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="../static/js/homework.js" type="text/javascript"></script>
    <script src="http://static.runoob.com/assets/jquery-validation-1.14.0/lib/jquery.js"></script>
    <script src="http://static.runoob.com/assets/jquery-validation-1.14.0/dist/jquery.validate.min.js"></script>
    <script src="https://static.runoob.com/assets/jquery-validation-1.14.0/dist/localization/messages_zh.js"></script>
    <link rel="stylesheet" href="../static/css/homework.css" type="text/css" />
</head>

<body>
    <header name="header" id="header">
        Account Register Page
    </header>
    <div name="basicData">
        <form name="sheet" id="sheet" ref="fileUpload" action="/upload" method="POST" enctype="multipart/form-data">
            <fieldset>
                <legend>基本資料</legend>
                <br>
                真實姓名:<input type="text" name="name" id="name">
                <br>
                使用者帳戶:
                <input type="text" name="username" id="username">
                <br>
                密碼:
                <input type="password" name="password" id="password">
                <br>
                請再輸入一次密碼:
                <input type="password" name="verifyPassword" id="verifyPassword">
                <br>
                性別：
                <select name="gender" id="gender">
                    <option value="0">男</option>
                    <option value="1">女</option>
                </select>
                <br>
                大頭貼：
                <input type="file" name="headShot" id="headShot" value="選擇檔案" accept="image/gif, image/jpeg, image/png">
                <img id="imgPreview" style="width: 200px;" src="#" />
                <br>
                Email:
                <input type="email" name="email" id="email">
                <br>
                安全問題:
                <select name="securityQ" id="securityQ">
                    <option value="0">最喜歡吃的食物?</option>
                    <option value="1">第一隻養的寵物名字?</option>
                    <option value="2">最常用的網路ID?</option>
                    <option value="3">就讀哪一所國中?</option>
                    <option value="4">幾歲時拿到第一台個人電腦?</option>
                </select>
                <br>
                安全問題答案:
                <input type="text" name="answer" id="answer">
            </fieldset>
            <div name="buttonArea" id="buttonArea">
                <input type="submit" class="buttonC" id="submit" value="送出">
                <input type="button" class="buttonC" id="clear_btn" value="清除">
                <input type="button" class="buttonC" value="填值">
            </div>

    </div>
    </form>
    <footer name="footer" id="footer">
        <div>
            copyright© 2020 JustBelieveMe All Rights Reserverd.
        </div>
    </footer>
</body>

</html>

```

By the way, I will got an error:

```
UnhandledPromiseRejectionWarning: Error: data and salt arguments required

```

but I think it is caused by the null value of the req.body that the hash doesn't work.