Joi as validation alternative in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import Joi for validation.

Express

const Joi = require('[1]');

Drag options to blanks, or click blank then click option'

Abody-parser

Bexpress

Cjoi

Dvalidator

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'joi' to import Joi.

Forgetting to install the 'joi' package before importing.

Joi is imported using the package name 'joi' to use its validation features.

2fill in blank

medium

Complete the code to define a Joi schema for a required string 'username'.

Express

const schema = Joi.object({ username: Joi.[1]().required() });

Drag options to blanks, or click blank then click option'

Astring

Barray

Cboolean

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using Joi.number() for a text field.

Omitting the required() method for mandatory fields.

Use Joi.string() to specify that 'username' must be a string.

3fill in blank

hard

Fix the error in validating the request body using Joi.

Express

const { error } = schema.[1](req.body);

Drag options to blanks, or click blank then click option'

AvalidateBody

Bcheck

Ctest

Dvalidate

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'validateBody' or 'check'.

Not destructuring the 'error' from the validation result.

The correct Joi method to validate data is 'validate'.

4fill in blank

hard

Fill both blanks to create a middleware that validates 'email' as a required string and calls next() if valid.

Express

const validateEmail = (req, res, next) => {
  const schema = Joi.object({ email: Joi.[1]().[2]() });
  const { error } = schema.validate(req.body);
  if (error) return res.status(400).send(error.details[0].message);
  next();
};

Drag options to blanks, or click blank then click option'

Astring

Brequired

Cnumber

Doptional

Attempts:

3 left

💡 Hint

Common Mistakes

Using Joi.number() for email.

Using optional() instead of required() for mandatory fields.

Use Joi.string() to specify the type and required() to make it mandatory.

5fill in blank

hard

Fill all three blanks to define a Joi schema for 'password' with minimum length 8, required, and validate it.

Express

const schema = Joi.object({ password: Joi.[1]().min([2]).[3]() });
const { error } = schema.validate(req.body);

Drag options to blanks, or click blank then click option'

Astring

B8

Crequired

Dnumber

Attempts:

3 left

💡 Hint

Common Mistakes

Using number() instead of string() for password.

Omitting required() making the field optional.

Setting min() to a wrong value or forgetting it.

Password should be a string, have a minimum length of 8, and be required.

Practice

1. What is the main purpose of using Joi in an Express application?

easy

A. To serve static files like images and CSS

B. To handle routing between different pages

C. To connect to a database

D. To validate incoming data and ensure it meets expected rules

Solution

1. Step 1: Understand Joi's role

   Joi is a library designed to check if data matches certain rules before using it.

2. Step 2: Compare with other Express tasks

   Routing, database connection, and serving files are handled by other parts of Express or middleware, not Joi.

3. Final Answer:

   To validate incoming data and ensure it meets expected rules -> Option D

4. Quick Check:

   Joi validates data = A [OK]

Hint: Joi is all about checking data rules fast [OK]

Common Mistakes:

• Confusing Joi with routing or database tools
• Thinking Joi serves files
• Assuming Joi manages app navigation

2. Which of the following is the correct way to define a Joi schema for a required string named username?

easy

A. const schema = Joi.string().required();

B. const schema = Joi.required().string();

C. const schema = Joi.string.required();

D. const schema = Joi.string().isRequired();

Solution

1. Step 1: Recall Joi syntax for strings

   Joi.string() creates a string schema, and .required() marks it as mandatory.

2. Step 2: Check method chaining order

   The correct chaining is Joi.string().required(), not Joi.required().string() or others.

3. Final Answer:

   const schema = Joi.string().required(); -> Option A

4. Quick Check:

   Joi.string().required() syntax = B [OK]

Hint: Use Joi.string().required() to make a string mandatory [OK]

Common Mistakes:

• Placing .required() before .string()
• Using .isRequired() which is not a Joi method
• Missing parentheses after string()

3. Given this Joi schema and data:

const schema = Joi.object({ age: Joi.number().min(18).required() });
const data = { age: 16 };
const result = schema.validate(data);

What will result.error contain?

medium

A. Null because Joi does not check numbers

B. Null because age is valid

C. An error object because age is less than 18

D. An error object because age is missing

Solution

1. Step 1: Understand the schema rules

   The schema requires age to be a number, at least 18, and present.

2. Step 2: Check the data against rules

   Data has age = 16, which is less than the minimum 18, so validation fails.

3. Final Answer:

   An error object because age is less than 18 -> Option C

4. Quick Check:

   Age 16 < 18 causes error = D [OK]

Hint: Min 18 means below 18 triggers error [OK]

Common Mistakes:

• Thinking 16 passes min(18)
• Assuming missing age error instead
• Believing Joi ignores number checks

4. You wrote this code to validate an email:

const schema = Joi.object({ email: Joi.string().email() });
const data = { email: 12345 };
const result = schema.validate(data);

What is the main problem here?

medium

A. The email method is missing parentheses

B. The email field is not a string, so validation fails

C. Joi.string() cannot be used with email validation

D. The schema object is missing .required()

Solution

1. Step 1: Check data type for email

   Email expects a string, but data has a number (12345), which is invalid.

2. Step 2: Confirm Joi email method usage

   Joi.string().email() is correct syntax; parentheses are present.

3. Final Answer:

   The email field is not a string, so validation fails -> Option B

4. Quick Check:

   Email must be string, got number = A [OK]

Hint: Email must be string, numbers cause validation error [OK]

Common Mistakes:

• Ignoring data type mismatch
• Thinking .email() needs no parentheses
• Assuming .required() is always needed

5. You want to validate a user object with name (string, required), age (optional number, min 0), and email (required valid email). Which Joi schema correctly enforces these rules?

hard

A. Joi.object({ name: Joi.string().required(), age: Joi.number().min(0), email: Joi.string().email().required() })

B. Joi.object({ name: Joi.string(), age: Joi.number().min(0).required(), email: Joi.string().email() })

C. Joi.object({ name: Joi.string().required(), age: Joi.number().min(0).required(), email: Joi.string().email() })

D. Joi.object({ name: Joi.string(), age: Joi.number(), email: Joi.string().email().required() })

Solution

1. Step 1: Check required fields

   Name and email must be required, so .required() must be on both.

2. Step 2: Check optional age with min 0

   Age is optional, so no .required(), but min(0) applies.

3. Step 3: Validate each option

   Joi.object({ name: Joi.string().required(), age: Joi.number().min(0), email: Joi.string().email().required() }) matches all rules exactly; others miss required or optional correctly.

4. Final Answer:

   Joi.object({ name: Joi.string().required(), age: Joi.number().min(0), email: Joi.string().email().required() }) -> Option A

5. Quick Check:

   Required name/email, optional age min 0 = C [OK]

Hint: Required fields get .required(), optional just rules [OK]

Common Mistakes:

• Marking optional age as required
• Missing .required() on name or email
• Confusing order of chaining methods