Express JS/MongoDB注册功能异常：页面持续刷新及端口占用问题

Hey, let's figure out why your registration form is causing endless refreshes and fix those issues step by step!

1. The Root Cause of Endless Refreshes: Mismatched Schema Fields & Missing Error Responses #

First off, the biggest issue here is a field mismatch between your User Schema and the data you're trying to save, which breaks the user creation process and leaves the browser hanging.

Look at your user.js Schema: you defined a required field called fullName, but in your users.js POST handler, you're pulling name from the request body and passing that to the new User() constructor. This means when you call newUser.save(), MongoDB will throw an error because the required fullName field is missing.

Worse, your catch block only logs the error to the console and doesn't send any response back to the browser. The request stays in a pending state, and browsers often retry such requests, leading to the endless refresh loop you're seeing.

Fix: Align the Schema and Request Data

You have two options here:

• Option 1: Update the Schema to match your form field

  // user.js
  const userSchema = new mongoose.Schema({
    name: { // Change `fullName` to `name`
      type: String,
      required: true
    },
    email: {
      type: String,
      required: true
    },
    password: {
      type: String,
      required: true
    },
    date: {
      type: Date,
      default: Date.now
    }
  });
  

• Option 2: Map the request name to the Schema's fullName

  // users.js
  const newUser = new User({ 
    fullName: name, // Map the incoming `name` to `fullName`
    email, 
    password 
  });
  

Add Proper Error Handling for Save Failures

Update the save() catch block to send a response to the browser instead of just logging:

newUser
  .save()
  .then(user => {
    req.flash(
      'success_msg',
      'You are now registered and can log in'
    );
    res.redirect('/users/login');
  })
  .catch(err => {
    console.log(err);
    errors.push({ msg: 'Failed to create your account. Please try again.' });
    res.render('register', { errors, name, email, password, password2 });
  });

2. Fix the Mongoose Connection Issue #

In your app.js, you defined the db variable with your MongoDB URI but passed an empty string to mongoose.connect(). While you said the connection log shows success (likely connecting to a default local instance), this is unreliable and could cause unexpected behavior later.

Update the connection code to use your db variable and add proper error handling:

// app.js
mongoose.connect(db, { useNewUrlParser: true, useUnifiedTopology: true })
  .then(() => console.log('MongoDB Connected...'))
  .catch(err => console.error('MongoDB connection failed:', err));

3. Resolve the EADDRINUSE Port Error #

This error just means port 8000 is already being used by another process. If it pops up again:

• Windows: Open Command Prompt and run:

  netstat -ano | findstr :8000
  # Find the PID number, then kill the process
  taskkill /PID <your-pid-number> /F
  

• Linux/macOS: Open Terminal and run:

  lsof -i :8000
  # Kill the process with the PID
  kill -9 <your-pid-number>
  

内容的提问来源于stack exchange，提问作者Leon Michalak