Display Flash Error Messages to User After Mongoose Model Save - node.js

Question

I have a page index.js which has a form to add users, and beside it a list of users in the database.
/routes/index.js
var express = require('express');
var router = express.Router();
var User = require('../schemas/user');
router.post('/create', function(req, res, next) {
var user = new User({
username: req.body.username,
email: req.body.email,
password: req.body.password
});
user.save(function(err) {
if (err) {
console.log('user save error ' + err.errmsg);
return res.json(err.errmsg);
}
res.redirect('/');
});
});
/* GET home page. */
router.get('/', function(req, res, next) {
User.find(function (err, users) {
if (err) {
console.log('get error ' + err);
//return res.sendStatus(500);
}
res.render(
'index',
{
userList : users
}
);
});
});
module.exports = router;
/schemas/user.js
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var userSchema = new Schema({
username: { type: String, required: true, unique: true },
email: { type: String, required: true, unique: true },
password: { type: String, required: true },
group: String,
created_at: Date,
updated_at: Date
});
var User = mongoose.model(
'User',
userSchema
);
module.exports = User;
Here is my view:
/views/index.pug
extends layout
block content
h1= title
p Welcome to #{title}
.container
.row
.col-sm
h1 Create User
form(
method='POST'
action='/create'
)
.form-group
label(for='username') Username:
input#username.form-control(
type='text',
placeholder='Enter username...',
name='username'
)
if usernameError
p.error= usernameError
.form-group
label(for='password') Password:
input#password.form-control(
type='password',
placeholder='Enter password...',
name='password'
)
if passwordError
p.error= passwordError
.form-group
label(for='email') Email:
input#email.form-control(
type='email',
placeholder='Enter email...',
name='email'
)
if emailError
p.error= emailError
button.btn.btn-primary(
type='submit',
) Submit
.col-sm
h2 User List
ul
each user in userList
li= user.username
As you can see, I have some conditionals in my index.pug file. What I want to do is if an error occurs I want to assign a message to a variable based on the error type (i.e. username already taken, or password too short) and pass that variable over to my pug view. The view will then render the message if the proper variable is set. Can somebody help me out? I'm mostly struggling with the fact that I also have to render the list of users, if I try to find users within the error catching part of the post node complains about headers already being set, i.e. If I have my router.post function like so:
router.post('/create', function(req, res, next) {
var user = new User({
username: req.body.username,
email: req.body.email,
password: req.body.password
});
user.save(function(err) {
if (err) {
console.log('user save error ' + err.errmsg);
User.find(function (err2, users) {
if (err2) {
console.log('get error ' + err2);
//return res.sendStatus(500);
}
res.render(
'index',
{
userList : users,
usernameError: err.errmsg
}
);
});
}
res.redirect('/');
});
});
Then I expect to see the usernameError message filled in my view but instead I get an error from the node server:
user save error E11000 duplicate key error collection: test.users index: username_1 dup key: { : "John" }
POST /create 302 71.995 ms - 46
Error: Can't set headers after they are sent.

Answer 1

username: { type: String, required: true, unique: true },
it's because unique true.
Error: Can't set headers after they are sent.
Error because you haven't return error. Whenever error occure simply return like
if (err) return next(err)
provided that you are using express centralized error handler
check last lines of your app.js.All errors from next(err) goes here
app.use(function(err, req, res, next) {
console.error( err);
..............
});