如何显示客户端用户已经存在 - MongoDB

Question

我正在使用MongoDB，NodeJS，ejs，passport等...

当我尝试使用数据库中已存在的用户名创建新用户时，我收到来自服务器端的错误

{ UserExistsError： 具有给定用户名的用户已 注册 at Promise.resolve.then.then.then (my/path/for/node_modules/passport-local-mongoose/index.js：238：17( 在 process._tickCallback (内部/进程/next_tick.js：68：7( 名称："用户存在错误"，消息："具有给定用户名的用户是 已注册' }

并且不要在客户端附加任何消息，只刷新页面并留在主页上，但不知道一个好方法，我希望客户端知道用户名已经被占用..

谢谢！

我的服务器端：

const express = require('express'),
passport = require('passport'),
User = require('../models/users.js'),
app = express.Router();

//Get User Data
exports.get_user_data = function(req, res) {
let userid = req.user._id;
User.findById(userid)
.exec((err, user) => {
if (err) {
console.log(err);
} else {
res.send(user);
}
});
}
//Render Register
exports.render_new_register = function(req, res) {
}
//Create New User Account
exports.create_new_account = function(req, res) {
User.register(new User({
username: req.body.username,
companyname: req.body.companyname,
companyimageURL: req.body.companyimageURL
}),
req.body.password,
(err, user) => {
if (err) {
console.log(err);
return res.redirect('/')
}
console.log("SUCCESS");
logUser(user, req, res);
}
)
};
//Render Login
exports.render_login_account = function(req, res) {
};
//Render Logout - end of user session 
exports.render_logout_account_endSession = function(req, res) {
req.logout();
res.redirect('/');
};
//Authenticate User Login
exports.user_login_authenticate =
passport.authenticate("local")

function logUser(user, req, res) {
req.login(user, (err) => {
if (err) {
console.log(err);
return res.redirect('/');
}
res.redirect('/dashboard') //register with success
})
}

我的客户端

<!-- Modal REGIST SIGNUP-->
<div class="modal fade" id="myModalRegist" tabindex="-1" role="dialog" aria-labelledby="modalLabel" aria-hidden="true">
<div class="modal-dialog" role="document">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-label="Close" style="outline: none; border: none">
<span style="outline: none; border: none" aria-hidden="true">&times;</span>
</button>
</div>
<div class="modal-body">
<div id="modal__header" class="container text-center">
<h1 class="modal__title">WELCOME</h1>
<p class="modal__paragraph"> Create a new account</p>
<form action="/getstarted" method="POST">
<div class="form-group">
<input type="text" class="form-control" aria-describedby="username" placeholder="enter username" name="username" required>
</div>
<div class="form-group">
<input id="passwordregist" type="password" class="form-control" placeholder="min 6 characters" required minlength="6" name="password">
</div>
<div class="form-group">
<input id="passwordregist_confirm" type="password" class="form-control" placeholder="min 6 characters" required minlength="6" name="password_confirm">
</div>
<div class="form-group">
<input type="companyname" class="form-control" placeholder="company name" name="companyname" required>
</div>
<div class="form-group">
<input type="companyimageURL" class="form-control" placeholder="company image URL" name="companyimageURL" required>
</div>
<div class="form-check">
<input type="checkbox" class="form-check-input" required>
<label class="form-check-label" for="check">Check me out</label>
<div id="alertconfirm"></div>
</div>
<button id="registersubmitbutton" type="submit" class="btn btn-default button_modal button_modal--colors">Get Started</button>
</form>
</div>
</div>
</div>
</div>
</div>
<!-- / Modal REGIST SIGNUP-->


<script>
$('#registersubmitbutton').on('click', function(e) {
let password = $("#passwordregist").val();
let password_confirm = $("#passwordregist_confirm").val();

if (password !== password_confirm) {
if ($('#alertconfirm').children().length === 0) {
$('#alertconfirm').append(
`<div class="alert" role="alert" style="font-size: 11px; color: #ec1818; padding: 0">
Oops! Passwords don't match. Please try again.</div>`
)
}
return false;
}
});
</script>

Answer 1

如果你想显示一条消息，你可能必须在你的点击方法中使用异步调用(我更喜欢创建一个onSubmit方法(，你可以使用AJAX来做请求。

以下是如何使用 POST 创建 AJAX 的示例： https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/send#Example_POST。

请记住，响应是对象xhr.responseText。

xhr.onreadystatechange = function() {
if(this.readyState == XMLHttpRequest.DONE && this.status == 200) {
console.log(xhr.responseText);
}
} 

另一方面，您必须更改 logUser 方法以返回有效的 JSON：

function logUser(user, req, res) {
req.login(user, (err) => {
if (err) {
return res.json({ error: error });
}
res.json({ error: null, message: "User registered" });
})
}

Answer 2

您可以通过用户名首先检查用户是否存在来实现

例：

userCtr.create_new_account = (req, res) => {
const {
username, companyname, companyimageURL
} = req.body;
const query = {
username: username 
}
User.findOne(query)
.then((user) => {
if (!user) {
//create User.
} else {
res.status(400).json({ error: 'user already exists' });
}
})
.catch((err) => {
//return error
});
};