Form validation styles in Bootsrap - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of form validation styles in Bootstrap?

Form validation styles in Bootstrap help visually indicate to users whether their input is valid or invalid, improving user experience and accessibility.

beginner

Which Bootstrap class adds a green border and check icon to a valid input field?

The class is-valid adds a green border and a check icon to indicate the input is valid.

beginner

Which Bootstrap class adds a red border and cross icon to an invalid input field?

The class is-invalid adds a red border and a cross icon to indicate the input is invalid.

beginner

How do you display a custom error message below an invalid input in Bootstrap?

Use a <div> with the class invalid-feedback immediately after the input field to show a custom error message.

intermediate

What attribute should be added to a form to enable Bootstrap's custom validation styles?

Add the novalidate attribute to the <form> element to disable native browser validation and use Bootstrap's custom styles.

Which class would you add to an input to show it is valid in Bootstrap?

A is-valid

B is-invalid

C valid-input

D input-valid

The is-valid class applies green border and check icon to valid inputs.

What class shows a red border and error icon for invalid inputs?

A invalid-feedback

B input-error

C is-invalid

D error-input

The is-invalid class styles inputs with a red border and error icon.

Where should you place the invalid-feedback element?

A Immediately after the input field

B Inside the input field

C Before the input field

D Anywhere in the form

The invalid-feedback element must be placed immediately after the input to show error messages properly.

What does the novalidate attribute do on a form?

A Enables native browser validation

B Adds Bootstrap validation styles automatically

C Prevents form submission

D Disables native browser validation

The novalidate attribute disables native browser validation so you can use custom Bootstrap validation.

Which icon appears with is-valid class in Bootstrap forms?

A Red cross

B Green checkmark

C Yellow warning

D Blue info

The is-valid class shows a green checkmark icon to indicate valid input.

Explain how to use Bootstrap classes to show valid and invalid form input states.

Think about the colors and icons that help users know if their input is correct.

Describe how to add custom error messages for invalid inputs using Bootstrap.

Where do you put the message and what class do you use?

Practice

1. Which Bootstrap class should you add to an input element to show it has valid data?

easy

A. valid-feedback

B. is-invalid

C. is-valid

D. invalid-feedback

Solution

1. Step 1: Understand Bootstrap validation classes

   Bootstrap uses is-valid to mark inputs as valid and is-invalid for invalid inputs.

2. Step 2: Identify the class for valid input

   The class is-valid visually marks the input as valid with green borders and icons.

3. Final Answer:

   is-valid -> Option C

4. Quick Check:

   Valid input class = is-valid [OK]

Hint: Valid input uses is-valid class for green highlight [OK]

Common Mistakes:

• Confusing is-valid with is-invalid
• Using feedback classes on input instead of messages
• Not adding any validation class

2. Which of the following is the correct way to add invalid feedback text below an input in Bootstrap?

easy

A. Error message

B. Error message

C. Error message

D. Error message

Solution

1. Step 1: Identify the correct feedback container

   Bootstrap uses invalid-feedback class inside a div to show invalid messages.

2. Step 2: Match the correct HTML structure

   The correct syntax is <div class="invalid-feedback">Message</div> placed after the input.

3. Final Answer:

   <div class="invalid-feedback">Error message</div> -> Option B

4. Quick Check:

   Invalid feedback uses div.invalid-feedback [OK]

Hint: Use div with invalid-feedback class for error messages [OK]

Common Mistakes:

• Using is-invalid class on feedback text instead of input
• Using valid-feedback class for invalid messages
• Placing feedback inside input tag

3. What will be the visual result of this code snippet?

<input type="text" class="form-control is-invalid" />
<div class="invalid-feedback">Please enter a valid name.</div>

medium

A. Input box with red border and error message below

B. Input box with green border and success message below

C. Input box with no border color change and no message

D. Input box with blue border and warning message below

Solution

1. Step 1: Analyze the input classes

   The input has is-invalid which applies a red border and error icon.

2. Step 2: Check the feedback message

   The invalid-feedback div shows the error message below the input in red text.

3. Final Answer:

   Input box with red border and error message below -> Option A

4. Quick Check:

   is-invalid + invalid-feedback = red error style [OK]

Hint: is-invalid input + invalid-feedback message = red error style [OK]

Common Mistakes:

• Confusing is-invalid with is-valid
• Expecting green border for is-invalid
• Missing feedback message display

4. Identify the error in this Bootstrap form validation snippet:

<input type="email" class="form-control" id="email" required>
<div class="valid-feedback">Looks good!</div>
<div class="invalid-feedback">Please enter a valid email.</div>

medium

A. The feedback messages should be inside the input tag

B. The required attribute is invalid in Bootstrap forms

C. The input type should be text instead of email

D. The input is missing is-valid or is-invalid class to show validation state

Solution

1. Step 1: Check validation classes on input

   The input lacks is-valid or is-invalid classes, so no visual feedback appears.

2. Step 2: Confirm feedback message placement and attributes

   Feedback messages are correctly placed outside input; required is valid HTML5 attribute.

3. Final Answer:

   The input is missing is-valid or is-invalid class to show validation state -> Option D

4. Quick Check:

   Validation classes needed on input for feedback display [OK]

Hint: Add is-valid or is-invalid class to input for feedback to show [OK]

Common Mistakes:

• Placing feedback inside input tag
• Removing required attribute thinking it's Bootstrap-only
• Using wrong input type for email

5. You want to create a form where the input shows green border and a success message only after the user submits valid data. Which Bootstrap classes and structure should you use?

hard

A. Add is-valid to input and place success message inside div.valid-feedback after input

B. Add is-invalid to input and place success message inside div.invalid-feedback

C. Add valid-feedback class to input and place message inside span

D. Add is-valid to input and place success message inside span.invalid-feedback

Solution

1. Step 1: Choose correct validation class for success

   Use is-valid on input to show green border and success icon.

2. Step 2: Place success message correctly

   Success message goes inside a div with class valid-feedback placed immediately after the input.

3. Final Answer:

   Add is-valid to input and place success message inside div.valid-feedback after input -> Option A

4. Quick Check:

   Success = is-valid + div.valid-feedback [OK]

Hint: Use is-valid on input and div.valid-feedback for success message [OK]

Common Mistakes:

• Mixing invalid classes with success messages
• Using span instead of div for feedback
• Placing feedback before input