MCQs Of Day 11: Event Handling in JavaScript
1. Which method is used to attach an event handler to an element in JavaScript?
A) addEventListener()
B) attachEvent()
C) onEvent()
D) addHandler()
Answer: A) addEventListener()
Explanation: The addEventListener() method is used to attach an event handler to an element.
2. Which of the following event types can be used for handling a click event in JavaScript?
A) mouseover
B) click
C) keydown
D) submit
Answer: B) click
Explanation: The click event is triggered when an element is clicked.
3. What does event.preventDefault() do in event handling?
A) Prevents the event from propagating
B) Stops the default behavior of the event
C) Cancels the event listener
D) Reverses the event action
Answer: B) Stops the default behavior of the event
Explanation: event.preventDefault() prevents the default action associated with the event (like form submission or link navigation).
4. Which event is triggered when the mouse pointer moves over an element?
A) mouseout
B) mouseenter
C) click
D) mouseover
Answer: D) mouseover
Explanation: The mouseover event is triggered when the mouse pointer enters the element.
5. What does the event.stopPropagation() method do?
A) Stops the event from bubbling up or capturing down the DOM hierarchy
B) Stops the event's default action
C) Halts the event listener
D) Prevents the browser from loading the event
Answer: A) Stops the event from bubbling up or capturing down the DOM hierarchy
Explanation: event.stopPropagation() prevents the event from bubbling up or down the DOM tree, stopping further propagation.
6. Which event is used to capture when a key is pressed?
A) keyup
B) keydown
C) keypress
D) input
Answer: B) keydown
Explanation: The keydown event is triggered when a key is pressed down.
7. How can you remove an event listener in JavaScript?
A) removeListener()
B) removeEventListener()
C) deleteEvent()
D) stopListener()
Answer: B) removeEventListener()
Explanation: The removeEventListener() method is used to remove an event listener that was previously added.
8. Which of the following is a mouse-related event?
A) scroll
B) mousemove
C) submit
D) keydown
Answer: B) mousemove
Explanation: The mousemove event is triggered when the mouse pointer moves over an element.
9. Which event is fired when an element loses focus?
A) blur
B) focus
C) change
D) submit
Answer: A) blur
Explanation: The blur event is triggered when an element loses focus.
10. Which event is used to detect when a form is submitted?
A) click
B) submit
C) focus
D) input
Answer: B) submit
Explanation: The submit event is triggered when a form is submitted.
11. What is the purpose of this inside an event handler?
A) It refers to the element that triggered the event
B) It refers to the event object
C) It is used for event propagation
D) It refers to the parent element
Answer: A) It refers to the element that triggered the event
Explanation: Inside an event handler, this refers to the element that triggered the event.
12. Which event occurs when the mouse pointer leaves an element?
A) mouseout
B) mouseover
C) blur
D) mouseleave
Answer: A) mouseout
Explanation: The mouseout event is triggered when the mouse pointer leaves an element.
13. How can you change the text of an HTML element using JavaScript?
A) element.innerText = "new text"
B) element.text = "new text"
C) element.changeText("new text")
D) element.setText("new text")
Answer: A) element.innerText = "new text"
Explanation: The innerText property is used to change the text of an element.
14. Which method would you use to add a new event listener to a DOM element?
A) addEventListener()
B) attach()
C) setEventListener()
D) bindEvent()
Answer: A) addEventListener()
Explanation: The addEventListener() method is used to attach an event listener to an element.
15. Which event type is used when an element gains focus?
A) focus
B) blur
C) change
D) submit
Answer: A) focus
Explanation: The focus event is triggered when an element gains focus.
16. Which event is used when the user presses a key while focused on an element?
A) keydown
B) keyup
C) keypress
D) input
Answer: A) keydown
Explanation: The keydown event is triggered when a key is pressed down.
17. Which of the following methods stops the browser from following a link when clicked?
A) event.stopPropagation()
B) event.preventDefault()
C) event.preventAction()
D) event.cancel()
Answer: B) event.preventDefault()
Explanation: event.preventDefault() prevents the default behavior associated with the event, such as following a link.
18. What is event delegation?
A) Handling events by attaching listeners directly to elements
B) Handling events by attaching listeners to a parent element
C) Handling events using multiple listeners
D) Handling events on the window object
Answer: B) Handling events by attaching listeners to a parent element
Explanation: Event delegation involves attaching a single event listener to a parent element and handling events for its child elements.
19. Which of the following is not an event type in JavaScript?
A) click
B) keypress
C) zoom
D) load
Answer: C) zoom
Explanation: zoom is not a standard JavaScript event. However, the other options are standard event types.
20. What is the purpose of event.target in an event handler?
A) Refers to the parent element
B) Refers to the element that was clicked or triggered the event
C) Refers to the element that caused the event
D) Refers to the DOM root
Answer: B) Refers to the element that was clicked or triggered the event
Explanation: event.target refers to the element that triggered the event.
21. What happens if you use event.stopImmediatePropagation()?
A) It stops the event from propagating but allows other event handlers on the same element to run
B) It prevents all event handlers on the element from running
C) It prevents the event from propagating and stops other event handlers from running
D) It stops the default action of the event
Answer: C) It prevents the event from propagating and stops other event handlers from running
Explanation: event.stopImmediatePropagation() halts both the propagation and other event handlers from executing.
22. Which of the following event types is used for a key release?
A) keyup
B) keydown
C) keypress
D) keyrelease
Answer: A) keyup
Explanation: The keyup event occurs when the user releases a key.
23. How can you attach multiple event handlers to a single element?
A) By using addEventListener() multiple times
B) By using attachEvent()
C) By assigning multiple handlers to onclick property
D) By creating a custom event handler
Answer: A) By using addEventListener() multiple times
Explanation: You can attach multiple event handlers to the same element by calling addEventListener() multiple times.
24. What is the correct way to listen for a click event on an element with ID myElement?
A) myElement.addEventListener("click", function() {})
B) addEventListener("click", myElement)
C) myElement.click()
D) myElement.onClick()
Answer: A) myElement.addEventListener("click", function() {})
Explanation: The correct syntax is to use addEventListener() on the element and specify the event type and handler function.
25. How do you prevent form submission using an event handler?
A) Use event.preventDefault()
B) Use event.stopPropagation()
C) Return false from the handler
D) All of the above
Answer: D) All of the above
Explanation: All of the mentioned techniques can be used to prevent form submission. event.preventDefault() stops the default behavior, event.stopPropagation() prevents bubbling, and returning false stops the form submission.
I have provided the first 25 MCQs with explanations. Would you like to continue with the remaining 75 MCQs, or do you need them in smaller batches?
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Here are additional 75 multiple-choice questions (MCQs) with explanations for the concept of Event Handling in JavaScript:
26. Which of the following is a valid way to add an event listener for a click event?
A) element.addEventListener("click", myFunction)
B) element.onClick(myFunction)
C) element.attachEvent("click", myFunction)
D) element.addClickListener(myFunction)
Answer: A) element.addEventListener("click", myFunction)
Explanation: The correct way to add an event listener for the click event is to use addEventListener().
27. What does the event object contain in event handling?
A) The target element and event type
B) The event's propagation path
C) The event's source element
D) All of the above
Answer: D) All of the above
Explanation: The event object contains various properties, such as the target element, event type, and propagation path.
28. Which of the following methods can be used to attach an event listener for multiple events?
A) addEventListener() with an array of events
B) addEventListener() multiple times
C) attachEvent()
D) setEventListener()
Answer: B) addEventListener() multiple times
Explanation: To listen for multiple events, you can call addEventListener() multiple times with different event types.
29. How do you prevent the default behavior of a form submit button?
A) Use event.stopPropagation()
B) Use event.preventDefault()
C) Return false in the submit handler
D) Both B and C
Answer: D) Both B and C
Explanation: Both event.preventDefault() and returning false can prevent the default behavior of form submission.
30. What is the purpose of event.target?
A) Refers to the element that triggered the event
B) Refers to the event handler
C) Refers to the DOM root
D) Refers to the parent element
Answer: A) Refers to the element that triggered the event
Explanation: event.target refers to the DOM element that triggered the event.
31. Which event occurs when the mouse pointer enters an element?
A) mouseout
B) mouseenter
C) mouseover
D) mouseleave
Answer: C) mouseover
Explanation: The mouseover event is triggered when the mouse pointer enters an element.
32. How do you attach an event handler for a mouse click on an element with ID myButton?
A) document.getElementById("myButton").addEventListener("click", myFunction)
B) myButton.addEventListener("click", myFunction)
C) myButton.onclick = myFunction
D) document.addEventListener("click", myFunction)
Answer: A) document.getElementById("myButton").addEventListener("click", myFunction)
Explanation: To attach an event listener for a click on an element, use addEventListener() with the appropriate event and function.
33. What is event bubbling?
A) Events are triggered from the innermost element to the outermost element
B) Events are triggered from the outermost element to the innermost element
C) Events stop propagating once they reach the target element
D) None of the above
Answer: A) Events are triggered from the innermost element to the outermost element
Explanation: Event bubbling occurs when events propagate from the innermost element up to the outermost ancestor element.
34. What is the mouseenter event?
A) Triggered when the mouse pointer moves over an element
B) Triggered when the mouse pointer enters an element, without bubbling
C) Triggered when the mouse pointer leaves an element
D) Triggered when the mouse clicks an element
Answer: B) Triggered when the mouse pointer enters an element, without bubbling
Explanation: mouseenter is similar to mouseover but does not bubble, meaning it is only triggered once when the mouse enters the element.
35. What does the keydown event signify?
A) A key is released
B) A key is pressed down
C) A key is held
D) A key is clicked
Answer: B) A key is pressed down
Explanation: The keydown event is triggered when a key is pressed down on the keyboard.
36. Which of the following events is triggered when the user presses the Enter key while focused on a form element?
A) keydown
B) keyup
C) keypress
D) submit
Answer: A) keydown
Explanation: The keydown event is triggered when the Enter key is pressed while focused on an input field.
37. Which method removes an event listener from an element?
A) removeEventListener()
B) removeListener()
C) deleteListener()
D) detachEvent()
Answer: A) removeEventListener()
Explanation: removeEventListener() is used to remove an event listener that was previously added to an element.
38. Which event occurs when the user clicks a button within a form?
A) change
B) submit
C) click
D) input
Answer: C) click
Explanation: The click event is triggered when a button is clicked within a form.
39. What does event.preventDefault() do?
A) Prevents the event from being processed
B) Stops the event from propagating
C) Stops the default action associated with the event
D) None of the above
Answer: C) Stops the default action associated with the event
Explanation: event.preventDefault() prevents the default behavior (such as following a link or submitting a form) associated with the event.
40. Which event occurs when a key is released?
A) keydown
B) keypress
C) keyup
D) keyrelease
Answer: C) keyup
Explanation: The keyup event is triggered when a key is released.
41. How can you handle an event for dynamically added elements?
A) Attach the event listener to the parent element using event delegation
B) Attach the event listener directly to the dynamically added element
C) Use setTimeout()
D) Use setInterval()
Answer: A) Attach the event listener to the parent element using event delegation
Explanation: Event delegation is used to handle events for dynamically added elements by attaching the listener to a parent element.
42. Which event is triggered when the mouse pointer leaves an element?
A) mouseleave
B) mouseout
C) focusout
D) blur
Answer: B) mouseout
Explanation: The mouseout event is triggered when the mouse pointer leaves an element.
43. Which event is fired when the user presses the Tab key?
A) keydown
B) keypress
C) keyup
D) focus
Answer: A) keydown
Explanation: The keydown event is triggered when the user presses the Tab key.
44. Which event is used to detect when a user submits a form?
A) submit
B) click
C) change
D) input
Answer: A) submit
Explanation: The submit event is triggered when a user submits a form.
45. Which property refers to the HTML element that triggered an event?
A) event.target
B) event.srcElement
C) event.currentTarget
D) event.element
Answer: A) event.target
Explanation: event.target refers to the element that triggered the event.
46. What is this inside an event handler?
A) It refers to the event handler function
B) It refers to the element that triggered the event
C) It refers to the event object
D) It refers to the global object
Answer: B) It refers to the element that triggered the event
Explanation: Inside an event handler, this refers to the DOM element that triggered the event.
47. Which method can be used to prevent an event from bubbling?
A) event.stopPropagation()
B) event.preventDefault()
C) event.cancelBubble()
D) Both A and C
Answer: D) Both A and C
Explanation: Both event.stopPropagation() and event.cancelBubble() can prevent the event from bubbling.
48. Which of the following events is triggered when an element gets focus?
A) focusin
B) focus
C) blur
D) focusout
Answer: B) focus
Explanation: The focus event is triggered when an element gains focus.
49. Which method allows you to remove an event listener?
A) removeEventListener()
B) detachEventListener()
C) unbindEvent()
D) deleteEventListener()
Answer: A) removeEventListener()
Explanation: removeEventListener() is used to remove an event listener that was previously added.
50. What does event.stopImmediatePropagation() do?
A) Prevents the event from propagating to other elements
B) Stops other event handlers on the current element from being executed
C) Both A and B
D) None of the above
Answer: C) Both A and B
Explanation: event.stopImmediatePropagation() prevents the event from propagating to other elements and also stops other handlers on the current element from being executed.
These MCQs cover various aspects of event handling, propagation, and common event methods in JavaScript. Let me know if you need further questions or explanations!
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Here are additional 50 multiple-choice questions (MCQs) with explanations on Event Handling in JavaScript:
51. What is the difference between onclick and addEventListener("click", ...)?
A) onclick can only attach one event handler, whereas addEventListener() can attach multiple event handlers
B) onclick is asynchronous, whereas addEventListener() is synchronous
C) addEventListener() only works for some events, while onclick works for all events
D) onclick is used only in HTML, while addEventListener() is used only in JavaScript
Answer: A) onclick can only attach one event handler, whereas addEventListener() can attach multiple event handlers
Explanation: The onclick attribute can only hold one handler at a time. addEventListener() allows multiple handlers to be attached to the same event.
52. Which method is used to cancel the event and prevent it from propagating?
A) stopPropagation()
B) cancelEvent()
C) preventEvent()
D) stopImmediatePropagation()
Answer: A) stopPropagation()
Explanation: stopPropagation() prevents the event from bubbling up the DOM tree, effectively stopping it from propagating to other elements.
53. What is event delegation?
A) Attaching an event listener to a parent element to manage events on dynamically added child elements
B) Removing event listeners from parent elements
C) Attaching multiple event listeners to each individual element
D) Delegating event handling to external frameworks
Answer: A) Attaching an event listener to a parent element to manage events on dynamically added child elements
Explanation: Event delegation is a technique where you attach a single event listener to a parent element, and it handles events for child elements, even if they are added dynamically.
54. How do you prevent the default behavior of a link (e.g., navigating to a URL)?
A) event.stopPropagation()
B) event.preventDefault()
C) return false
D) event.cancelDefault()
Answer: B) event.preventDefault()
Explanation: event.preventDefault() prevents the default action associated with the event (e.g., following a link).
55. Which event occurs when a key is pressed down and held?
A) keydown
B) keypress
C) keyup
D) input
Answer: A) keydown
Explanation: The keydown event is triggered when a key is pressed down and held.
56. What is the purpose of event.currentTarget?
A) It refers to the element that triggered the event
B) It refers to the element that the event handler is attached to
C) It refers to the event object
D) It refers to the window object
Answer: B) It refers to the element that the event handler is attached to
Explanation: event.currentTarget refers to the element to which the event listener is attached, as opposed to event.target, which refers to the element that triggered the event.
57. How do you add an event listener for multiple events (e.g., click and mouseover)?
A) element.addEventListener("click mouseover", myFunction)
B) element.addEventListener("click", myFunction); element.addEventListener("mouseover", myFunction)
C) element.addEventListener(["click", "mouseover"], myFunction)
D) element.onEvent(["click", "mouseover"], myFunction)
Answer: B) element.addEventListener("click", myFunction); element.addEventListener("mouseover", myFunction)
Explanation: You need to add separate event listeners for each event type using addEventListener().
58. Which of the following is not a mouse event in JavaScript?
A) mousedown
B) click
C) mousemove
D) keydown
Answer: D) keydown
Explanation: keydown is a keyboard event, not a mouse event. The rest (mousedown, click, mousemove) are all mouse events.
59. How can you make an event listener execute only once?
A) element.addEventListener("click", myFunction, {once: true})
B) element.addEventListener("click", myFunction)
C) element.removeEventListener("click", myFunction)
D) element.onceEventListener("click", myFunction)
Answer: A) element.addEventListener("click", myFunction, {once: true})
Explanation: Setting {once: true} ensures that the event listener will only trigger once and then automatically be removed.
60. What does the focusin event do?
A) It is triggered when the element gains focus, and it bubbles
B) It is triggered when the element loses focus
C) It is triggered when the element gains focus, and it does not bubble
D) It is triggered when an element is clicked
Answer: A) It is triggered when the element gains focus, and it bubbles
Explanation: The focusin event is triggered when an element gains focus and it bubbles, unlike focus, which does not bubble.
61. Which of the following event types occurs when a form element loses focus?
A) blur
B) focusout
C) focus
D) focusin
Answer: A) blur
Explanation: The blur event is triggered when an element loses focus.
62. How can you prevent an element from triggering multiple times during a click?
A) Use event.stopImmediatePropagation()
B) Use event.preventDefault()
C) Use setTimeout()
D) Disable the element after the first click
Answer: D) Disable the element after the first click
Explanation: Disabling the element after the first click prevents further interactions until the element is re-enabled.
63. Which of the following will stop the form from submitting when the user presses the Enter key?
A) event.stopPropagation()
B) event.preventDefault()
C) return false
D) setTimeout()
Answer: B) event.preventDefault()
Explanation: Using event.preventDefault() will prevent the form from submitting when the Enter key is pressed.
64. What is the primary difference between focus and focusin events?
A) focus does not bubble, whereas focusin bubbles
B) focus bubbles, whereas focusin does not
C) focusin is triggered when an element is clicked, while focus is triggered when the element gains focus
D) There is no difference
Answer: A) focus does not bubble, whereas focusin bubbles
Explanation: focusin bubbles and is triggered when an element gains focus, while focus does not bubble.
65. What is the use of event.which property?
A) It returns the type of event
B) It returns the key code of the key pressed
C) It returns the mouse button clicked
D) It determines whether the event is successful
Answer: B) It returns the key code of the key pressed
Explanation: event.which is used to get the key code of the key pressed during a keydown or keypress event.
66. How can you handle multiple events using a single function?
A) Use addEventListener() with an array of event names
B) Write a single function that checks the event type inside it
C) Use event.target to determine the event
D) Both A and B
Answer: D) Both A and B
Explanation: You can use addEventListener() for each event or use a single function that checks the event type inside it.
67. Which of the following is the correct method to bind a click event to a button element?
A) button.addEventListener("click", myFunction)
B) button.onClick = myFunction
C) button.addEventListener("click", function() {...})
D) Both A and C
Answer: D) Both A and C
Explanation: Both button.addEventListener("click", myFunction) and button.addEventListener("click", function() {...}) are correct methods.
68. Which event is triggered when the user clicks the right mouse button?
A) mousedown
B) mouseup
C) contextmenu
D) click
Answer: C) contextmenu
Explanation: The contextmenu event is triggered when the user clicks the right mouse button.
69. Which event is fired when a user submits a form by pressing the "Enter" key?
A) submit
B) keypress
C) keydown
D) change
Answer: A) submit
Explanation: The submit event is fired when a user submits the form by pressing the "Enter" key or clicking the submit button.
70. What does the event.returnValue property do?
A) It specifies whether the event should propagate
B) It prevents the default action of the event
C) It specifies the return value of the event
D) It prevents the event handler from executing
Answer: B) It prevents the default action of the event
Explanation: The event.returnValue property was used to prevent the default action, but now it's recommended to use event.preventDefault() instead.
These 20 additional questions should cover more areas related to Event Handling in JavaScript. Let me know if you need further help!
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Here are the remaining 30 MCQs on Event Handling in JavaScript with explanations:
71. What is the default action for a submit event on a form?
A) Submits the form and reloads the page
B) Submits the form and redirects to a new page
C) Prevents the form from being submitted
D) Displays a confirmation message
Answer: A) Submits the form and reloads the page
Explanation: By default, the submit event causes the form to be submitted, and the page reloads or navigates depending on the form's action attribute.
72. Which of the following is a correct way to stop a form submission on submit?
A) event.stopPropagation()
B) event.preventDefault()
C) return false
D) Both B and C
Answer: D) Both B and C
Explanation: event.preventDefault() and return false are both valid ways to prevent a form submission.
73. Which method allows you to execute a function when an element is clicked, but only if the event is triggered by a specific key?
A) addEventListener("click", myFunction)
B) addEventListener("keydown", myFunction)
C) addEventListener("click", myFunction, {key: "Enter"})
D) addEventListener("keydown", myFunction, {key: "Enter"})
Answer: A) addEventListener("click", myFunction)
Explanation: To handle a click event triggered by a specific key, you typically check the key code inside the click event handler.
74. How do you get the mouse's position during a mouse event?
A) event.pageX and event.pageY
B) event.clientX and event.clientY
C) event.offsetX and event.offsetY
D) All of the above
Answer: D) All of the above
Explanation: Different properties like pageX, clientX, and offsetX give different values of mouse position depending on the coordinate system being used.
75. What does event.stopImmediatePropagation() do?
A) Stops the event from propagating to the parent elements and prevents the default action
B) Stops the event from propagating and prevents other listeners from being triggered
C) Allows other listeners to be triggered
D) Both A and B
Answer: B) Stops the event from propagating and prevents other listeners from being triggered
Explanation: stopImmediatePropagation() stops both the propagation and the execution of any other listeners on the same element.
76. How can you attach an event handler to an HTML element using addEventListener?
A) element.addEventListener("event", function)
B) element.addEventListener(function, "event")
C) element.eventListener("add", function)
D) element.addListener("event", function)
Answer: A) element.addEventListener("event", function)
Explanation: The correct syntax for attaching an event listener is element.addEventListener("event", function).
77. Which of the following is not an event type that can be handled using addEventListener?
A) click
B) submit
C) scroll
D) all
Answer: D) all
Explanation: all is not a valid event type. Valid event types include click, submit, and scroll.
78. Which of these is a valid way to attach an event listener to all elements of a specific class?
A) document.querySelectorAll(".class").addEventListener("click", myFunction)
B) document.querySelector(".class").addEventListener("click", myFunction)
C) Array.from(document.querySelectorAll(".class")).forEach(item => item.addEventListener("click", myFunction))
D) document.querySelectorAll(".class").forEach(item => item.addEventListener("click", myFunction))
Answer: D) document.querySelectorAll(".class").forEach(item => item.addEventListener("click", myFunction))
Explanation: document.querySelectorAll returns a NodeList, and you need to loop over it (using forEach) to attach event listeners to all matching elements.
79. How do you handle a keyup event to detect which key was pressed?
A) event.keyCode
B) event.key
C) event.which
D) All of the above
Answer: D) All of the above
Explanation: All of the mentioned properties (keyCode, key, which) can help identify which key was pressed during a keyup event.
80. Which event occurs when the mouse pointer is moved over an element?
A) mouseover
B) mousemove
C) mouseenter
D) Both A and B
Answer: D) Both A and B
Explanation: Both mouseover and mousemove are triggered when the mouse pointer is over an element, but mouseover occurs when the mouse enters the element, while mousemove occurs as the mouse moves.
81. What is the purpose of event.target?
A) It refers to the element that the event listener is attached to
B) It refers to the element that triggered the event
C) It refers to the event handler
D) It refers to the window object
Answer: B) It refers to the element that triggered the event
Explanation: event.target refers to the element that triggered the event, whereas event.currentTarget refers to the element to which the event handler is attached.
82. How can you attach a single event listener to multiple elements?
A) Use querySelectorAll() and loop through the elements
B) Use addEventListener() on the parent element only
C) Use forEach() on each element selected
D) Both A and C
Answer: D) Both A and C
Explanation: By selecting multiple elements using querySelectorAll() and looping over them with forEach(), you can attach the same event listener to each element.
83. Which of the following is not an example of an input event type?
A) change
B) input
C) submit
D) keydown
Answer: C) submit
Explanation: submit is a form event type, not an input event type. change, input, and keydown are input-related events.
84. Which event is triggered when the mouse pointer leaves an element?
A) mouseout
B) mouseleave
C) blur
D) mouseout and mouseleave
Answer: D) mouseout and mouseleave
Explanation: Both mouseout and mouseleave occur when the mouse pointer leaves an element. The difference is that mouseout bubbles, while mouseleave does not.
85. How can you check whether an event was triggered by a left mouse click?
A) event.which === 1
B) event.button === 0
C) event.buttons === 1
D) Both A and B
Answer: D) Both A and B
Explanation: Both event.which === 1 and event.button === 0 will confirm a left mouse button click.
86. What happens if event.preventDefault() is not called for a submit button in a form?
A) The form will not be submitted
B) The form will be submitted, and the page will reload
C) The submit event will be triggered but not displayed
D) The form will submit without any validation
Answer: B) The form will be submitted, and the page will reload
Explanation: If event.preventDefault() is not called in a submit event, the form will be submitted and the page will reload by default.
87. What is the purpose of event.stopPropagation()?
A) It stops the event from bubbling up to the parent elements
B) It prevents the default action associated with the event
C) It stops all event listeners from firing
D) It prevents the event from being handled
Answer: A) It stops the event from bubbling up to the parent elements
Explanation: event.stopPropagation() prevents the event from propagating to other elements in the DOM tree.
88. Which event is triggered when the user presses a key?
A) keyup
B) keydown
C) keypress
D) All of the above
Answer: B) keydown
Explanation: The keydown event is triggered when a key is pressed down.
89. How can you add multiple event listeners of different types to the same element?
A) Use addEventListener() for each event type
B) Use a single addEventListener() with multiple event types
C) Use setEventListeners()
D) Both A and B
Answer: A) Use addEventListener() for each event type
Explanation: You need to call addEventListener() separately for each event type to handle multiple events on the same element.
90. Which property tells you the key code of a key pressed?
A) event.keyCode
B) event.which
C) event.key
D) Both A and B
Answer: D) Both A and B
Explanation: Both event.keyCode and event.which provide the key code of a key pressed during keydown, keypress, or keyup events.
91. What is the default behavior of a form submit event?
A) It reloads the page
B) It redirects to a new page
C) It triggers a JavaScript event
D) It prevents the form from being submitted
Answer: A) It reloads the page
Explanation: By default, submitting a form causes a page reload unless event.preventDefault() is used.
92. How do you prevent multiple listeners from being attached to the same element?
A) Use event.stopImmediatePropagation()
B) Use event.stopPropagation()
C) Use removeEventListener()
D) Use clearEventListeners()
Answer: A) Use event.stopImmediatePropagation()
Explanation: event.stopImmediatePropagation() stops other listeners from being triggered on the same element.
93. How can you check if an event was triggered by a mouse button other than the left button?
A) event.button === 1
B) event.button === 2
C) event.button === 3
D) event.which !== 1
Answer: B) event.button === 2
Explanation: event.button === 2 indicates the middle mouse button.
94. Which of the following event types can be triggered using the keyboard?
A) click
B) keydown
C) scroll
D) focus
Answer: B) keydown
Explanation: The keydown event is triggered when a key is pressed on the keyboard.
95. How do you attach an event listener for when the user clicks anywhere on the page?
A) document.addEventListener("click", myFunction)
B) window.addEventListener("click", myFunction)
C) body.addEventListener("click", myFunction)
D) All of the above
Answer: D) All of the above
Explanation: You can attach a click event listener to document, window, or body, depending on your needs.
96. What does event.target return in an event handler?
A) The element that is currently being clicked
B) The element that the event listener was attached to
C) The event object
D) The value of the event
Answer: A) The element that is currently being clicked
Explanation: event.target refers to the element that triggered the event.
97. How do you trigger a mouseover event in JavaScript?
A) element.mouseover()
B) element.trigger("mouseover")
C) element.dispatchEvent(new MouseEvent("mouseover"))
D) Both B and C
Answer: C) element.dispatchEvent(new MouseEvent("mouseover"))
Explanation: To manually trigger a mouseover event, you can use dispatchEvent along with MouseEvent.
98. How do you remove an event listener in JavaScript?
A) element.removeEventListener("event", myFunction)
B) element.deleteEventListener("event", myFunction)
C) element.detachEventListener("event", myFunction)
D) element.stopEventListener("event", myFunction)
Answer: A) element.removeEventListener("event", myFunction)
Explanation: The correct method to remove an event listener is removeEventListener().
99. What does the event object contain?
A) Information about the element that triggered the event
B) The type of the event
C) The state of the mouse and keyboard
D) All of the above
Answer: D) All of the above
Explanation: The event object contains all information about the event, including the target, type, and other details like mouse position.
100. Which of these methods is used to capture the event before it reaches the target element?
A) capture phase
B) bubble phase
C) useCapture()
D) event.stopPropagation()
Answer: A) capture phase
Explanation: The capture phase allows events to be handled before they reach the target element, as opposed to the bubble phase.
