MCQs Of Day 24
JavaScript and Forms
Section
1: Basics of JavaScript and Forms
1. What does
the getElementById method do?
o
A) Finds all elements by class name
o
B) Finds an element by its ID
o
C) Finds all elements by tag name
o
D) Finds elements by their type
Answer: B
Explanation: getElementById is used to access a single element with a
specific ID.
2. Which
event is commonly used to trigger form validation before submission?
o
A) onmouseover
o
B) onsubmit
o
C) onchange
o
D) onreset
Answer: B
Explanation: The onsubmit event is fired when a form is submitted,
making it ideal for validation.
3. Which
method prevents the default action of a form submission?
o
A) stopPropagation()
o
B) preventDefault()
o
C) haltEvent()
o
D) stopDefault()
Answer: B
Explanation: preventDefault() prevents the browser’s default behavior,
such as submitting the form.
4. What
property of an input element retrieves its value?
o
A) text
o
B) innerHTML
o
C) value
o
D) content
Answer: C
Explanation: The value property is used to retrieve or set the value of
an input element.
5. Which of
the following is a valid JavaScript way to select all input fields in a form?
o
A) document.querySelectorAll("input")
o
B) document.getElementsByClassName("input")
o
C) document.getInputByType("all")
o
D) document.inputSelector("all")
Answer: A
Explanation: querySelectorAll selects all elements matching the given
selector.
Section
2: Accessing Form Elements
6. Which
property accesses the form element's name attribute?
o
A) form.name
o
B) form[0]
o
C) form["name"]
o
D) form.elements["name"]
Answer: D
Explanation: elements provides a collection of all form controls,
accessible by their name.
7. How can
you access the first form on a webpage?
o
A) document.forms[1]
o
B) document.forms.first()
o
C) document.forms[0]
o
D) document.getFirstForm()
Answer: C
Explanation: document.forms returns an array-like collection of all
forms, starting at index 0.
8. What does
form.elements.length return?
o
A) The total number of forms on the page
o
B) The total number of elements in the form
o
C) The total number of input fields on the page
o
D) The number of submit buttons in the form
Answer: B
Explanation: The elements collection contains all elements of a form,
and length returns their count.
Section
3: Validating Form Input
9. Which
JavaScript function checks if a field is empty?
o
A) isEmptyField()
o
B) input.trim() === ""
o
C) field.clear()
o
D) field.isEmpty()
Answer: B
Explanation: Trimming whitespace and comparing to an empty string
ensures no characters are present.
10.
Which method can check if an email input value is
valid?
o
A) isEmail()
o
B) test() with a regex
o
C) validateEmail()
o
D) checkInput("email")
Answer: B
Explanation: Regular expressions (regex) are commonly used to validate
email format.
11.
What property checks the validity of a form
element?
o
A) checkValidity()
o
B) isValid()
o
C) validate()
o
D) form.valid
Answer: A
Explanation: checkValidity() is a built-in method for form validation.
Section
4: Preventing Form Submission
12.
How do you stop a form from submitting?
o
A) Call return false inside the onsubmit handler
o
B) Use stopSubmit()
o
C) Remove the action attribute
o
D) Use form.preventSubmit()
Answer: A
Explanation: Returning false in the onsubmit event handler stops
submission.
13.
Which of the following prevents default behavior?
o
A) form.reset()
o
B) form.validate()
o
C) event.preventDefault()
o
D) stopPropagation()
Answer: C
Explanation: event.preventDefault() is specifically designed to stop the
default action.
Section
5: Real-World Scenarios
14.
How can you enable or disable a submit button based
on input validation?
o
A) By toggling the readonly property of the button
o
B) By setting button.disabled to true or false
o
C) By hiding the button element using CSS
o
D) By using form.hideSubmit()
Answer: B
Explanation: The disabled property of a button can be dynamically set.
15.
What does pattern attribute in input fields do?
o
A) Specifies a regex for validation
o
B) Limits the number of characters
o
C) Specifies placeholder text
o
D) Sets a default value
Answer: A
Explanation: The pattern attribute allows you to define regex for input
validation.
16.
How would you reset all form fields in JavaScript?
o
A) form.clear()
o
B) form.elements.reset()
o
C) form.reset()
o
D) document.clearForm()
Answer: C
Explanation: The reset() method clears all user input in a form.
Section
6: Dynamic Feedback
17.
Which event is suitable for providing real-time
feedback while a user types?
o
A) onchange
o
B) onblur
o
C) onkeyup
o
D) onsubmit
Answer: C
Explanation: The onkeyup event is triggered every time the user releases
a key, enabling real-time feedback.
18.
How can you display an error message next to an
invalid field?
o
A) Use alert()
o
B) Add an error message to a sibling element using
JavaScript
o
C) Redirect to another page
o
D) Use the browser’s default error handling
Answer: B
Explanation: Dynamically updating a sibling element is a user-friendly
way to show errors.
These are the first 18 MCQs,
organized into meaningful sections. Let me know if you'd like the remaining
questions structured similarly, or if you have preferences for specific
subtopics within JavaScript and Forms!
4o
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Here are more MCQs for JavaScript
and Forms, continuing from where we left off:
Section
7: Advanced Accessing Form Elements
19.
Which method retrieves form data from a form
element in JSON format?
o
A) JSON.stringify(form)
o
B) new FormData(form)
o
C) form.toJSON()
o
D) document.serialize(form)
Answer: B
Explanation: FormData is used to collect data from forms, which can be
converted to JSON using custom logic.
20.
How do you get the value of a selected option in a
dropdown?
o
A) dropdown.selectedIndex
o
B) dropdown.options[dropdown.selectedIndex].value
o
C) dropdown.text
o
D) dropdown.selectedOption
Answer: B
Explanation: This accesses the options array of the dropdown and
retrieves the value of the selected option.
21.
What property identifies whether a checkbox is
checked?
o
A) checkbox.selected
o
B) checkbox.isChecked
o
C) checkbox.checked
o
D) checkbox.status
Answer: C
Explanation: The checked property of a checkbox element determines its
state.
22.
How do you access the action URL of a form in
JavaScript?
o
A) form.getAttribute('action')
o
B) form.action
o
C) document.getFormAction()
o
D) form.url
Answer: B
Explanation: The action property of a form element contains the URL
where the form data is submitted.
23.
What happens if you don’t set a method attribute on
a form?
o
A) Form submission fails
o
B) The method defaults to POST
o
C) The method defaults to GET
o
D) The form uses an invalid method
Answer: C
Explanation: If the method attribute is not specified, it defaults to GET.
Section
8: Form Validation with JavaScript
24.
Which method ensures a user enters a value in a
required field?
o
A) Add the required attribute in HTML
o
B) Use if (input.value !== "") in
JavaScript
o
C) Use input.checkValidity() in JavaScript
o
D) All of the above
Answer: D
Explanation: Any of these methods can ensure a required field is filled.
25.
What does the novalidate attribute in a <form>
tag do?
o
A) Enables HTML5 validation
o
B) Disables browser-based validation
o
C) Clears form inputs after submission
o
D) Validates the form dynamically
Answer: B
Explanation: The novalidate attribute prevents the browser from
performing default HTML5 form validation.
26.
What is the correct way to validate a number input
field?
o
A) Use the type="number" attribute in
HTML
o
B) Use JavaScript to check if Number(input.value)
is valid
o
C) Use a regex to validate the input
o
D) All of the above
Answer: D
Explanation: All these methods are valid approaches for validating
numeric input.
27.
How can you set a custom error message for an
invalid field in JavaScript?
o
A) input.error = "Error message"
o
B) input.setCustomValidity("Error
message")
o
C) input.validateMessage = "Error
message"
o
D) input.checkValidity("Error message")
Answer: B
Explanation: The setCustomValidity() method allows you to define a
custom error message.
28.
What does the maxlength attribute do in an input
field?
o
A) Restricts the number of characters that can be
entered
o
B) Validates the input length dynamically
o
C) Removes extra characters automatically
o
D) Limits the output of the input
Answer: A
Explanation: The maxlength attribute ensures users cannot input more
than the specified number of characters.
Section
9: Preventing Form Submission
29.
How can you ensure a form submits only if all
fields are valid?
o
A) Add return false to invalid fields
o
B) Use event.preventDefault() on invalid fields
o
C) Check each field's validity using checkValidity()
before allowing submission
o
D) Use CSS to highlight invalid fields
Answer: C
Explanation: Using checkValidity() ensures only valid inputs are
submitted.
30.
Which of the following can prevent form submission?
o
A) JavaScript logic in the onsubmit handler
o
B) Using event.preventDefault()
o
C) Returning false in the submit handler
o
D) All of the above
Answer: D
Explanation: All these methods can stop form submission based on conditions.
31.
What happens when you prevent the default
submission behavior of a form?
o
A) The form reloads the page
o
B) The form clears all inputs
o
C) The browser doesn’t send form data to the server
o
D) The form action URL is executed without sending
data
Answer: C
Explanation: Preventing default submission stops the browser from
sending data to the server.
Section
10: Real-World Scenarios
32.
What is the best way to validate a password field?
o
A) Check for a minimum length using minlength
o
B) Use regex to enforce a combination of characters
o
C) Use JavaScript to match against required rules
o
D) All of the above
Answer: D
Explanation: Combining all these methods ensures robust password
validation.
33.
How do you dynamically change an input field to readonly?
o
A) input.readOnly = true
o
B) input.setAttribute('readonly', true)
o
C) input.disable()
o
D) A and B
Answer: D
Explanation: Both readOnly and setAttribute can make a field readonly
dynamically.
34.
Which attribute ensures a dropdown always starts
with a default option?
o
A) default
o
B) selected
o
C) placeholder
o
D) value
Answer: B
Explanation: The selected attribute sets the default selected option in
a dropdown.
35.
How would you style invalid fields dynamically?
o
A) Add an invalid class using JavaScript
o
B) Use the :invalid CSS pseudo-class
o
C) Highlight using inline styles
o
D) All of the above
Answer: D
Explanation: These approaches can be combined to visually indicate
invalid fields.
Continuation
Let me know if you'd like me to
keep adding more or tailor the questions toward a specific subtopic!
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Here’s a continuation of MCQs
on JavaScript and Forms:
Section
11: Advanced Form Validation
36.
Which method is best to validate an email field in
JavaScript?
o
A) Use type="email" in the HTML input tag
o
B) Use a regex pattern to match email formats
o
C) Use the checkValidity() method
o
D) All of the above
Answer: D
Explanation: All these methods can validate email input; combining them
ensures more robust validation.
37.
What does the pattern attribute do in an HTML form
input?
o
A) Restricts input to match a specified regular
expression
o
B) Formats the input dynamically
o
C) Ensures only numbers are entered
o
D) Prevents empty inputs
Answer: A
Explanation: The pattern attribute validates the input against a
provided regular expression.
38.
What will input.validity.valid return for an
invalid required input field?
o
A) true
o
B) false
o
C) null
o
D) undefined
Answer: B
Explanation: The validity.valid property returns false if the field is
invalid.
39.
Which of the following is NOT a part of the validity
property in JavaScript?
o
A) valueMissing
o
B) typeMismatch
o
C) minLengthError
o
D) patternMismatch
Answer: C
Explanation: The minLengthError is not a predefined property of the validity
object.
40.
How do you validate the length of a string entered
into a text field?
o
A) Use the maxlength attribute in HTML
o
B) Use JavaScript to check input.value.length
o
C) Combine HTML and JavaScript validation
o
D) All of the above
Answer: D
Explanation: Both HTML attributes and JavaScript can be used to validate
input length effectively.
Section
12: Preventing Form Submission - Advanced
41.
Which JavaScript event is fired during a form
submission?
o
A) onchange
o
B) onsubmit
o
C) onload
o
D) onclick
Answer: B
Explanation: The onsubmit event triggers when the form is submitted.
42.
What is the purpose of the return false statement
in a form submit handler?
o
A) Stops JavaScript execution
o
B) Prevents form submission
o
C) Validates the form
o
D) Clears form inputs
Answer: B
Explanation: Returning false in the submit handler stops the default
submission action.
43.
Which method allows validation to occur before
submission?
o
A) Adding validation logic inside the onsubmit
event
o
B) Using form.onvalidate
o
C) Triggering input.validate()
o
D) Adding return true in the handler
Answer: A
Explanation: Adding logic inside the onsubmit event ensures validation
happens before submission.
44.
Which of these does NOT prevent form submission?
o
A) event.preventDefault()
o
B) Returning false from a submit handler
o
C) An input field with readonly attribute
o
D) Adding validation conditions in the onsubmit
event
Answer: C
Explanation: The readonly attribute disables editing but does not stop
submission.
45.
How do you prevent submission when the form is
invalid?
o
A) Add onsubmit="return validateForm()"
o
B) Use event.preventDefault()
o
C) Both A and B
o
D) Set form.submit = false
Answer: C
Explanation: Combining return validateForm() and event.preventDefault()
is a robust way to prevent invalid form submission.
Section
13: Real-World Scenarios
46.
What is the best way to display error messages for
invalid fields dynamically?
o
A) Use alert()
o
B) Create a <span> or <div> for error
messages and update its content
o
C) Log errors in the console
o
D) Change the field’s background color only
Answer: B
Explanation: Dynamically updating the DOM to show error messages
provides a better user experience.
47.
How do you clear all inputs in a form using
JavaScript?
o
A) form.clear()
o
B) form.reset()
o
C) form.elements.reset()
o
D) form.clearInputs()
Answer: B
Explanation: The reset() method clears all input fields to their initial
values.
48.
What attribute would you use to allow multiple
files to be selected in a file input?
o
A) multi
o
B) multiple
o
C) allow-multi
o
D) file-multiple
Answer: B
Explanation: The multiple attribute allows users to select multiple
files.
49.
Which method allows retrieving all selected options
in a multi-select dropdown?
o
A) select.options
o
B) Array.from(select.selectedOptions)
o
C) select.getSelected()
o
D) select.selected
Answer: B
Explanation: The selectedOptions property contains a collection of all
selected options.
50.
How would you validate that two password fields
match before submission?
o
A) Compare their value properties in JavaScript
o
B) Use the pattern attribute in HTML
o
C) Add type="password-match" to the
second field
o
D) Use regex to compare both fields
Answer: A
Explanation: Comparing the value of both fields in JavaScript ensures
they match.
Let me know if you'd like me to
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Here’s a continuation of MCQs
on JavaScript and Forms:
Section
14: Accessing Form Elements
51.
What property is used to access the value of an
input field in JavaScript?
o
A) input.text
o
B) input.value
o
C) input.content
o
D) input.data
Answer: B
Explanation: The value property of an input element provides or sets the
current value of the field.
52.
What does the document.forms property return?
o
A) A list of all form values
o
B) A collection of all form elements in the
document
o
C) An array of input fields in a form
o
D) The default form submission URL
Answer: B
Explanation: The document.forms property returns a collection of all <form>
elements in the document.
53.
How do you access an element in a form by its name
attribute?
o
A) form.getElementByName()
o
B) form[name]
o
C) form.elements[name]
o
D) form.querySelector(name)
Answer: C
Explanation: You can access an element by its name using the form.elements[name]
syntax.
54.
Which method retrieves the value of a selected
radio button in a form?
o
A) form.getValue(radio)
o
B) Loop through all radio buttons and check checked
property
o
C) radioGroup.value
o
D) Use the radioGroup.getSelected() method
Answer: B
Explanation: To retrieve the value of a selected radio button, loop
through the group and check which one is checked.
55.
What happens if form.submit() is called directly in
JavaScript?
o
A) The form validation is ignored
o
B) Validation runs as usual
o
C) The form resets
o
D) The browser displays a warning
Answer: A
Explanation: Calling form.submit() bypasses built-in validation and
submits the form directly.
Section
15: Common Errors and Debugging
56.
What error occurs when trying to access a
non-existent form field?
o
A) ReferenceError
o
B) TypeError
o
C) UndefinedError
o
D) It returns undefined without an error
Answer: D
Explanation: Accessing a non-existent form field returns undefined but
does not throw an error.
57.
What will document.getElementById("form1").submit();
do if form1 has invalid fields?
o
A) Prevent submission until errors are resolved
o
B) Submit the form without validation
o
C) Throw a validation error
o
D) Log the validation errors in the console
Answer: B
Explanation: The submit() method ignores validation and submits the
form.
58.
Which console log helps in debugging form
validation?
o
A) console.error(form.errors)
o
B) console.log(input.validity)
o
C) console.debug(input.errors)
o
D) console.warn(form.validation)
Answer: B
Explanation: Logging the validity object helps to identify why a field
is invalid.
59.
What does a patternMismatch validity state
indicate?
o
A) The input does not match the required regex
pattern
o
B) The input length exceeds the maximum allowed
o
C) The input is empty
o
D) The field type is incorrect
Answer: A
Explanation: The patternMismatch state is triggered when input does not
match the pattern regex.
60.
What should be done if a form validation script is
not working?
o
A) Use alert() for debugging
o
B) Check if onsubmit is correctly assigned
o
C) Ensure event listeners are attached after the
DOM loads
o
D) All of the above
Answer: D
Explanation: Debugging steps include checking script logic, event
attachment, and browser console.
Section
16: Cross-Browser Compatibility
61.
Which validation method is NOT supported by older
browsers?
o
A) HTML5 attributes like required
o
B) JavaScript validation scripts
o
C) addEventListener for form events
o
D) DOM manipulation
Answer: A
Explanation: HTML5 form attributes like required may not work in
outdated browsers.
62.
What should you use for backward compatibility with
HTML5 form validation?
o
A) Fallback JavaScript validation scripts
o
B) Ignore validation for old browsers
o
C) Rely on server-side validation only
o
D) Use custom form libraries
Answer: A
Explanation: JavaScript can be used as a fallback for browsers that do
not support HTML5 validation.
63.
Which method ensures consistent validation across
all browsers?
o
A) HTML5 validation only
o
B) JavaScript-only validation
o
C) Combining HTML5 and JavaScript validation
o
D) Relying on server-side validation
Answer: C
Explanation: Combining both methods ensures consistent user experience
and robust validation.
64.
How do polyfills help with form validation?
o
A) They add custom validation styles
o
B) They mimic missing features in older browsers
o
C) They simplify HTML code
o
D) They validate forms on the server
Answer: B
Explanation: Polyfills emulate missing browser features to support
modern functionality.
65.
What is the purpose of using novalidate on a form?
o
A) Disables default HTML5 validation
o
B) Allows JavaScript to handle all validation
o
C) Prevents form submission
o
D) Both A and B
Answer: D
Explanation: The novalidate attribute disables HTML5 validation,
enabling custom JavaScript validation.
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Here’s a continuation with more
MCQs focused on JavaScript and Forms:
Section
17: Preventing Form Submission
66.
Which of the following can be used to prevent a
form from submitting when a button is clicked?
o
A) event.preventDefault()
o
B) form.preventSubmit()
o
C) return false;
o
D) Both A and C
Answer: D
Explanation: Both event.preventDefault() and return false; prevent the
default form submission behavior.
67.
What is the purpose of event.preventDefault() in
form validation?
o
A) To cancel the form submission if there are
validation errors
o
B) To submit the form asynchronously
o
C) To prevent the page from reloading
o
D) To display a success message
Answer: A
Explanation: event.preventDefault() is used to stop form submission if
validation fails.
68.
How can form submission be triggered manually after
validation passes?
o
A) form.submit()
o
B) form.submitForm()
o
C) form.dispatchEvent(new Event('submit'))
o
D) Both A and C
Answer: D
Explanation: form.submit() or triggering a custom submit event can
manually submit the form after validation.
69.
If you have an onsubmit event handler in
JavaScript, what is the return value of the handler if you want to allow the
form to submit?
o
A) false
o
B) undefined
o
C) true
o
D) event.preventDefault()
Answer: C
Explanation: Returning true from the onsubmit handler allows the form to
submit. Returning false prevents it.
70.
Which JavaScript event should be used to capture
form submission before it happens?
o
A) onclick
o
B) onsubmit
o
C) oninput
o
D) onchange
Answer: B
Explanation: The onsubmit event is triggered when the user submits the
form, allowing you to intervene before submission.
Section
18: Form Validation Using JavaScript
71.
Which attribute is used to specify the minimum
number of characters for a text input?
o
A) minlength
o
B) min-length
o
C) min
o
D) length
Answer: A
Explanation: The minlength attribute specifies the minimum number of
characters required in an input field.
72.
How can you check if a text input is empty using
JavaScript?
o
A) if (input.value == '')
o
B) if (input == '')
o
C) if (input.value == null)
o
D) if (input == null)
Answer: A
Explanation: Checking input.value == '' verifies if the input field is
empty.
73.
Which method can you use to check if a checkbox is
checked in JavaScript?
o
A) input.checked()
o
B) input.isChecked()
o
C) input.checked
o
D) input.selected
Answer: C
Explanation: The checked property of a checkbox element returns true if
the checkbox is selected.
74.
How do you make sure that a radio button group has
been selected?
o
A) Check input.checked for each radio button
o
B) Use input.selected for the group
o
C) Use input.isSelected() method
o
D) Use input.value of the first radio button
Answer: A
Explanation: To validate that a radio button group is selected, you must
check the checked property of each button in the group.
75.
Which of the following is the correct way to
validate a form using required attribute in HTML5?
o
A) Add required to the input field in the HTML
o
B) Add required to the input field using JavaScript
o
C) Use input.required == true in JavaScript
o
D) Use input.checkValidity() in JavaScript
Answer: A
Explanation: The required attribute in HTML5 makes the input field
mandatory to fill out before submission.
Section
19: Handling Form Inputs
76.
What does the input.type property return?
o
A) The current value of the input
o
B) The type of the input element (e.g., text,
checkbox)
o
C) The name of the input field
o
D) The default value of the input
Answer: B
Explanation: The input.type property returns the type of the input
element (e.g., text, number, radio, checkbox).
77.
What is the purpose of the input.setCustomValidity()
method?
o
A) To reset form validation
o
B) To add a custom error message when the input is
invalid
o
C) To clear the form input value
o
D) To set the input type
Answer: B
Explanation: The setCustomValidity() method is used to set a custom
error message for invalid input.
78.
Which method checks whether the input value is
valid according to its type and constraints?
o
A) input.checkValidity()
o
B) input.isValid()
o
C) input.valid()
o
D) input.validate()
Answer: A
Explanation: The checkValidity() method checks whether the input
satisfies the validation constraints like required, minlength, etc.
79.
Which JavaScript method is used to get the selected
option from a <select> dropdown?
o
A) select.getSelectedOption()
o
B) select.selected
o
C) select.selectedIndex
o
D) select.selectedOption
Answer: C
Explanation: The selectedIndex property returns the index of the
selected option in a <select> dropdown.
80.
Which JavaScript function is used to get the value
of a <textarea> element?
o
A) textarea.value()
o
B) textarea.text()
o
C) textarea.getValue()
o
D) textarea.value
Answer: D
Explanation: The value property is used to get or set the content of a <textarea>
element.
Section
20: Preventing Duplicate Submissions
81.
Which of the following is the best way to prevent
duplicate form submissions?
o
A) Disable the submit button after the first click
o
B) Use submit.prevent() method
o
C) Set a timeout before the second submission
o
D) Automatically reset the form after submission
Answer: A
Explanation: Disabling the submit button prevents the user from clicking
it multiple times before the form is processed.
82.
What happens if a form is submitted and the submit
button is clicked twice?
o
A) The form will submit twice
o
B) The form will show an error
o
C) The second click will be ignored if the button
is disabled
o
D) It will reset the form
Answer: C
Explanation: Disabling the submit button after the first click ensures
that the form is only submitted once.
83.
What would be a good approach to prevent accidental
form submission by pressing the Enter key?
o
A) Disable the Enter key on the form
o
B) Use event.preventDefault() on the form's submit
event
o
C) Use input.removeAttribute('required')
o
D) Use input.blur() when the Enter key is pressed
Answer: B
Explanation: Preventing the form submission with event.preventDefault()
on submit ensures that accidental submissions are avoided.
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MCQs focused on JavaScript and Forms, continuing from where we left off:
Section
21: Working with Form Elements
84.
Which of the following methods can be used to
access an individual form element by its name attribute?
o
A) document.getElementByName('elementName')
o
B) document.getElementById('elementName')
o
C) document.forms['formName']['elementName']
o
D) document.querySelector('#elementName')
Answer: C
Explanation: The correct way to access an individual form element by its
name is document.forms['formName']['elementName'].
85.
How can you retrieve the value of a radio button
group in JavaScript?
o
A) document.getElementByName('groupName').value
o
B) document.getElementById('groupName').value
o
C) document.querySelectorAll('input[name="groupName"]')
o
D) document.getElementById('groupName').checked
Answer: A
Explanation: To get the value of the selected radio button from a group,
use document.getElementByName('groupName').value.
86.
What will the reset() method do to a form in
JavaScript?
o
A) Reset the form values to their default state
o
B) Submit the form automatically
o
C) Trigger a custom validation
o
D) Re-render the form HTML
Answer: A
Explanation: The reset() method will reset the form fields to their
initial default values.
87.
How can you access the value of a checkbox in
JavaScript?
o
A) checkbox.checked
o
B) checkbox.value
o
C) checkbox.isSelected()
o
D) checkbox.status
Answer: A
Explanation: The checked property of a checkbox returns true if it is
checked, otherwise false.
88.
What is the return type of the document.forms
property in JavaScript?
o
A) HTMLFormElement
o
B) HTMLCollection
o
C) NodeList
o
D) Array
Answer: B
Explanation: The document.forms property returns an HTMLCollection of
all the form elements in the document.
Section
22: Form Validation and Error Handling
89.
What is the role of input.setCustomValidity() in
form validation?
o
A) It triggers the validation process
o
B) It prevents form submission
o
C) It displays a custom error message
o
D) It removes the input field from validation
Answer: C
Explanation: The setCustomValidity() method sets a custom error message
for form validation.
90.
Which event handler is used to check form
validation before submission in JavaScript?
o
A) onchange
o
B) onsubmit
o
C) onblur
o
D) oninput
Answer: B
Explanation: The onsubmit event is used to handle form validation before
submission.
91.
How can you check if a form input is valid using
JavaScript?
o
A) input.isValid()
o
B) input.checkValidity()
o
C) input.validity()
o
D) input.validate()
Answer: B
Explanation: The checkValidity() method returns true if the input meets
all validation constraints, otherwise false.
92.
Which of the following methods can be used to reset
the form's validation state?
o
A) form.resetValidation()
o
B) form.clear()
o
C) form.reset()
o
D) form.resetForm()
Answer: C
Explanation: The reset() method resets all form fields and clears any
validation messages.
93.
What is the purpose of the input.validity property?
o
A) To check if the input value is valid according
to its constraints
o
B) To set the validity state of the input
o
C) To trigger the validation process manually
o
D) To set a custom error message for invalid input
Answer: A
Explanation: The validity property is used to access the input's
validity state (e.g., valid, tooShort, typeMismatch, etc.).
Section
23: Custom Validation Messages
94.
What should be the return value of a custom
validation function to indicate a valid input?
o
A) true
o
B) false
o
C) null
o
D) An empty string ""
Answer: A
Explanation: Returning true from a custom validation function indicates
that the input is valid.
95.
Which method is used to add a custom error message
for a form element?
o
A) setCustomMessage()
o
B) setCustomValidity()
o
C) setErrorMessage()
o
D) showError()
Answer: B
Explanation: The setCustomValidity() method is used to set a custom
error message for an input element.
96.
Which of the following is true about the input.validity
property?
o
A) It can only be checked on textarea inputs
o
B) It contains boolean values indicating validation
status
o
C) It contains an object with different error types
for invalid input
o
D) It is read-only and cannot be modified
Answer: C
Explanation: The validity property is an object that contains various
error types for invalid input (e.g., valueMissing, typeMismatch).
Section
24: Form Submission and Processing
97.
Which method is used to manually submit a form in
JavaScript after validation?
o
A) form.submit()
o
B) form.send()
o
C) form.trigger()
o
D) form.submitForm()
Answer: A
Explanation: The submit() method is used to manually submit a form after
all validations are passed.
98.
How can you prevent the default action of form
submission in JavaScript?
o
A) event.preventDefault()
o
B) event.stopPropagation()
o
C) form.prevent()
o
D) form.stop()
Answer: A
Explanation: The event.preventDefault() method prevents the default form
submission action.
99.
If you want to check the validity of all the form
inputs before submission, which method would you use?
o
A) form.validity()
o
B) form.checkValidity()
o
C) form.isValid()
o
D) form.validate()
Answer: B
Explanation: The checkValidity() method checks the validity of all form
inputs and returns true if all inputs are valid.
100.
Which of the following attributes can be used to
trigger form validation when the user submits the form?
- A) validate
- B) validation
- C) novalidate
- D) submitValidation
Answer: C
Explanation: The novalidate attribute is used to disable automatic form
validation on form submission.
