Mongoose (validation + hooks = 🔥)

How mongoose inbuilt validations and hooks can be powerful at times and much more

Photo by Manuel Sardo on Unsplash

Mongoose is an ODM(Object Document Modeler) for the mongo DB database. It provides ease such as built-in casting, query building, validations, and more.

Validations

You must have used joi for schema validation in express, but why to use heavy packages such as joi if we can validate using mongoose, now we will see how to use the mongoose validate function to validate schemas.

Here I have created a simple route to register a new user:

// *NEW USER ROUTE
app.post("/register", async (req, res) => {
try {
const user = await User.create(req.body);
res.json({ success: true, message: "User saved successfuly!!" });
} catch (e) {
return res.status(400).json({ success: false, messge: e.message });
}
});

User Model:

const mongoose = require("mongoose");
const bcrypt = require("bcryptjs");
const User = new mongoose.Schema({
name: {
type: String,
required: true,
},
email: {
type: String,
required: true,
unique: true,
},
phone: {
type: String,
required: true,
},
password: {
type: String,
required: true
},
});
module.exports = mongoose.model("user", User);

If you want custom error messages:

....
required: [true, "phone number is required"]
....

Note: unique is not a validator

Adding validation

Mongoose uses an inbuilt validation function that validates the schema and also returns a custom message.

(ps: validating contact length)

“Entered input is passed to the message as an argument”

phone: {
type: String,
required: [true, "Phone number is required !"],
validate: {
validator: (v) => {
return v.length == 10;
},
message: (props) => props.value + " Must be 10 digits !",
},
},

Using regex :

email: {
type: String,
required: [true, "email is required !!"],
unique: true,
validate: {
validator: (email) => {
const pattern = /^[A-Z0-9._%+-]+@([A-Z0-9-]+\.)+[A-Z]{2,4}$/i;
return pattern.test(email);
},
message: (props) => `${props.value} is not in correct format !!`,
},
},

Now, while creating a new user you need not to worry about validation, mongoose will handle and throw validations, accordingly !!

Postman screenshot

Similarly when using incorrect email:

Postman Screenshot

Et voila! Goodbye, joi.

Next Step: Using mongoose hooks

There are mainly two mongoose hooks that are widely used:

• “pre”: does Something before saving the model.
• “post”: does something after saving the model.

Using hooks/middlewares:

If we console log this inside pre hook, we get the req.body or what the user entered.

Let's hash the password before saving it to the database using bcrypt library.

as pre is a middleware, it takes next as an argument and can also return promises, after successful completion, it calls next() middleware.

Let’s see if that worked …

Now our password is hash and we didn’t do any changes to our controller.

Similarly post hook works after saving the model.

Events that middleware can take:

• “save”
• “remove”
• “validate”

And more.

Final source code: link

If you have reached here, thank you for reading this article I hope it clears the use of mongoose validations and middle-wares/hooks. If you liked it don’t forget to leave an applaud.

Thank you!

Photo by Kelly Sikkema on Unsplash