Improve mongoose validation error handling - node.js

Question

I have the following schema with required validations:
var mongoose = require("mongoose");
var validator = require("validator");
var userSchema = new mongoose.Schema(
{
email: {
type: String,
required: [true, "Email is a required field"],
trim: true,
lowercase: true,
unique: true,
validate(value) {
if (!validator.isEmail(value)) {
throw new Error("Please enter a valid E-mail!");
}
},
},
password: {
type: String,
required: [true, "Password is a required field"],
validate(value) {
if (!validator.isLength(value, { min: 6, max: 1000 })) {
throw Error("Length of the password should be between 6-1000");
}
if (value.toLowerCase().includes("password")) {
throw Error(
'The password should not contain the keyword "password"!'
);
}
},
},
},
{
timestamps: true,
}
);
var User = mongoose.model('User', userSchema);
I pass the email and password through a form by sending post request using the following route:
router.post("/user", async (req, res) => {
try {
var user = new User(req.body);
await user.save();
res.status(200).send(user);
} catch (error) {
res.status(400).send(error);
}
});
module.exports = mongoose.model("User", user);
Whenever I enter a field against the validation rules, I get a very long error message, which is obvious. But now, I want to improve the error handling so that it gets easy to interpret for the users. Rather than redirecting to a generic error page, how can I redirect to the same signup page and display the flash messages near the incorrect fields telling about the error? And also on success, something similar should be done, like a green flash message on the top.
I am using ejs for my signup pages.

Answer 1

In the catch block, you can check if the error is a mongoose validation error, and dynamically create an error object like this:
router.post("/user", async (req, res) => {
try {
var user = new User(req.body);
await user.save();
res.status(200).send(user);
} catch (error) {
if (error.name === "ValidationError") {
let errors = {};
Object.keys(error.errors).forEach((key) => {
errors[key] = error.errors[key].message;
});
return res.status(400).send(errors);
}
res.status(500).send("Something went wrong");
}
});
When we send a request body like this:
{
"email": "test",
"password": "abc"
}
Response will be:
{
"email": "Please enter a valid E-mail!",
"password": "Length of the password should be between 6-1000"
}

Answer 2

you can use validator like this instead of throwing an error :
password:{
type:String,
required:[true, "Password is a required field"],
validate: {
validator: validator.isLength(value,{min:6,max:1000}),
message: "Length of the password should be between 6-1000"
}
}

Answer 3

you can send
res.status(400).send(error.message);
instead of :
res.status(400).send(error);
and you should make some changes in Schema also.
validate(value){
if (!validator.isEmail(value)) {
throw new Error("Please enter a valid E-mail!");
}
}
with
validate: [validator.isEmail, "Please enter a valid E-mail!" ]
and for password:
minlength: 6,
maxlength:1000,
validate:{
validator: function(el){
return el.toLowerCase() !== "password"
}
message: 'The password should not contain the keyword "password"!'
}

Answer 4

If you are using mongoose then you can catch error easily using this method for signup route, by chaining if and else condition depending on your error methods
try {
} catch (error) {
console.log(error);
if (error.errors) {
if (error.errors.password) {
//if password is less than 6 characters
return res.status(400).json(error.errors.password.message)
}
if (error.errors.email) {
//if email is not in correct format. i'm using validator package
return res.status(400).json(error.errors.email.message)
}
} else {
return res.status(400).json(error.message)
}
}
if found simpler one here..
try { } catch (error) {
console.log(error);
// checking validation
if (error.name === "ValidationError") {
const message = Object.values(error.errors).map(value => value.message);
return res.status(400).json({
error: message
})
}
res.status(400).json(error.message)
}
}