MCQs Of Day 23: JavaScript Timing Events
1. What
is the purpose of the setTimeout() function in JavaScript?
A) It runs a function at a
specified time
B) It runs a function repeatedly at a specified interval
C) It schedules a function to run after a specified delay
D) It stops all running functions
Answer: C) It
schedules a function to run after a specified delay.
Explanation: The
setTimeout() function is used to execute a function after a specified delay,
measured in milliseconds.
2. What
will setInterval() do in JavaScript?
A) Executes a function only once
B) Executes a function repeatedly after a specified delay
C) Clears an interval
D) Pauses the execution of functions
Answer: B)
Executes a function repeatedly after a specified delay.
Explanation: The
setInterval() function runs the specified function at regular intervals
(repeatedly) after a delay.
3. What
will happen if you use clearTimeout() with an invalid timer ID?
A) The function will stop
executing immediately
B) An error will be thrown
C) It will have no effect
D) The function will execute again
Answer: C) It
will have no effect.
Explanation: If
clearTimeout() is used with an invalid timer ID (e.g., a timer that doesn't
exist), it does nothing.
4. How do
you stop a running interval?
A) Using stopInterval()
B) Using clearInterval()
C) Using clearTimeout()
D) Using setInterval() with a negative value
Answer: B) Using
clearInterval().
Explanation: To stop
an interval, use the clearInterval() function, passing the interval ID returned
by setInterval().
5. How
can you delay a function call by 2 seconds?
A) setInterval(myFunction, 2000)
B) setTimeout(myFunction, 2000)
C) delayFunction(myFunction, 2000)
D) executeFunction(myFunction, 2000)
Answer: B)
setTimeout(myFunction, 2000).
Explanation: The
setTimeout() function is used to delay the execution of a function for a
specified period (in this case, 2 seconds).
6. Which
method allows you to execute a function once after a delay?
A) setInterval()
B) setTimeout()
C) clearInterval()
D) clearTimeout()
Answer: B)
setTimeout().
Explanation: The
setTimeout() method is used to execute a function only once after a specified
delay.
7. How
would you stop a function set by setInterval() after 10 seconds?
A) clearInterval()
B) clearTimeout()
C) stopInterval()
D) setTimeout(clearInterval(), 10000)
Answer: A)
clearInterval().
Explanation: To stop
a function running repeatedly with setInterval(), use clearInterval() along
with the timer ID.
8. Which
method is used to get the unique ID of a timeout or interval?
A) timerID()
B) setInterval()
C) setTimeout()
D) Both setTimeout() and setInterval() return an ID.
Answer: D) Both
setTimeout() and setInterval() return an ID.
Explanation: Both
setTimeout() and setInterval() return a unique ID which can be used to stop the
timer or interval with clearTimeout() or clearInterval() respectively.
9. What
is the minimum delay time in JavaScript for setTimeout() and setInterval()?
A) 1 millisecond
B) 4 milliseconds
C) 0 milliseconds
D) 10 milliseconds
Answer: B) 4
milliseconds.
Explanation: Both
setTimeout() and setInterval() have a minimum delay time of approximately 4
milliseconds, though it may be rounded to the nearest available value depending
on the browser.
10. What
happens when the delay parameter in setTimeout() is set to 0?
A) It executes the function
immediately
B) It waits for the next event loop
C) It causes an infinite loop
D) It throws an error
Answer: B) It
waits for the next event loop.
Explanation: A delay
of 0 milliseconds tells the browser to execute the function after the current
call stack has cleared, i.e., on the next event loop iteration.
11. Which
of the following is true about setInterval()?
A) It stops automatically after a
specified time
B) It can be stopped by clearTimeout()
C) It executes a function once after the specified interval
D) It runs a function repeatedly at the specified interval
Answer: D) It
runs a function repeatedly at the specified interval.
Explanation:
setInterval() repeatedly runs a function after a specified interval until it is
stopped with clearInterval().
12. How
do you clear a timeout in JavaScript?
A) clearInterval()
B) clearTimeout()
C) stopTimeout()
D) stopInterval()
Answer: B)
clearTimeout().
Explanation: The
clearTimeout() function is used to stop a timeout set by setTimeout().
13. How
can you stop an interval that has been set?
A) clearTimeout()
B) stopInterval()
C) clearInterval()
D) stopTimer()
Answer: C)
clearInterval().
Explanation: To stop
a repeating interval set by setInterval(), you use clearInterval() with the
interval ID.
14. What
is the default value of the delay parameter in setTimeout() if it's not
provided?
A) 0 milliseconds
B) 4 milliseconds
C) 1000 milliseconds
D) 100 milliseconds
Answer: A) 0
milliseconds.
Explanation: If the
delay value is not provided, setTimeout() defaults to a delay of 0
milliseconds, meaning the function will execute as soon as the current
execution context is cleared.
15. What
will the following code snippet do?
javascript
Copy code
let id =
setInterval(function() {
console.log("Hello");
}, 1000);
clearInterval(id);
A) It will print
"Hello" once
B) It will print "Hello" every second
C) It will print "Hello" once and stop
D) It will not print anything
Answer: A) It
will print "Hello" once.
Explanation: The
clearInterval(id) stops the interval immediately after it starts, so
"Hello" is printed only once.
16. What
does setInterval() return?
A) The time interval in
milliseconds
B) A unique ID for the interval
C) The function to execute
D) The delay time in milliseconds
Answer: B) A
unique ID for the interval.
Explanation:
setInterval() returns a unique ID that can be used with clearInterval() to stop
the interval.
17. Which
of the following methods is used to clear an interval in JavaScript?
A) stopInterval()
B) clearTimeout()
C) clearInterval()
D) cancelInterval()
Answer: C)
clearInterval().
Explanation: The
clearInterval() function is used to stop an interval that was previously set
using setInterval().
18. What
is the result of this code?
javascript
Copy code
setTimeout(()
=> console.log("One second passed"), 1000);
A) "One second passed"
will be printed immediately
B) "One second passed" will be printed after 1000 milliseconds
C) The function will never execute
D) "One second passed" will be printed every second
Answer: B)
"One second passed" will be printed after 1000 milliseconds.
Explanation: The
function inside setTimeout() will be executed after 1000 milliseconds, printing
the message once.
19. What
does clearInterval() do?
A) Stops a single timeout
function
B) Stops a recurring interval function
C) Starts a new timeout
D) Pauses the current execution
Answer: B) Stops
a recurring interval function.
Explanation:
clearInterval() stops the interval that was previously set with setInterval().
20. How
can you execute a function every 3 seconds using JavaScript?
A) setInterval(function, 3000)
B) setTimeout(function, 3000)
C) clearInterval(function, 3000)
D) clearTimeout(function, 3000)
Answer: A)
setInterval(function, 3000).
Explanation:
setInterval() is used to execute a function repeatedly after every specified
interval (3000 milliseconds or 3 seconds in this case).
21. What
is the result of the following code?
javascript
Copy code
let
timeoutID = setTimeout(function() {
console.log("Delayed");
}, 0);
clearTimeout(timeoutID);
A) It prints "Delayed"
after 0 milliseconds
B) It prints "Delayed" immediately
C) It never prints anything
D) It throws an error
Answer: C) It
never prints anything.
Explanation: The
clearTimeout(timeoutID) call cancels the timeout before it can execute.
22. Which
method would you use to delay a function call by 5 seconds?
A) setTimeout(myFunction, 5000)
B) setInterval(myFunction, 5000)
C) setTimeout(myFunction)
D) clearTimeout(myFunction)
Answer: A)
setTimeout(myFunction, 5000).
Explanation: To delay
the function call for 5 seconds, use setTimeout() with 5000 milliseconds as the
delay.
23. What
is the purpose of clearTimeout() in JavaScript?
A) It stops a function set by
setInterval()
B) It stops a function set by setTimeout()
C) It pauses the execution of a function
D) It starts a new timeout
Answer: B) It
stops a function set by setTimeout().
Explanation: The
clearTimeout() function cancels a timeout that was set with setTimeout().
24. How
can you execute a function after the current script has finished executing, but
before the next event loop iteration?
A) setInterval(function, 0)
B) setTimeout(function, 0)
C) clearTimeout(function)
D) clearInterval(function)
Answer: B)
setTimeout(function, 0).
Explanation: Using
setTimeout() with a 0-millisecond delay will execute the function as soon as
the current execution context is cleared, i.e., in the next event loop.
25. What
will the following code do?
javascript
Copy code
let
counter = 0;
let
intervalID = setInterval(function() {
counter++;
console.log(counter);
if (counter === 5) {
clearInterval(intervalID);
}
}, 1000);
A) It prints 1, 2, 3, 4, 5 at
1-second intervals
B) It prints "5" repeatedly
C) It prints 1, 2, 3, 4, 5 immediately
D) It throws an error
Answer: A) It
prints 1, 2, 3, 4, 5 at 1-second intervals.
Explanation: The code
uses setInterval() to increment the counter every second and prints it. Once
the counter reaches 5, clearInterval() stops the interval.
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to JavaScript Timing Events:
26. Which
method is used to clear an interval timer in JavaScript?
A) clearTimeout()
B) cancelInterval()
C) clearInterval()
D) stopInterval()
Answer: C)
clearInterval().
Explanation: To stop
an interval that was set using setInterval(), you use clearInterval() and pass
the interval ID.
27. What
does the following code snippet do?
javascript
Copy code
let
timeoutID = setTimeout(function() {
console.log("First message");
}, 500);
clearTimeout(timeoutID);
A) Prints "First
message" after 500 milliseconds
B) Prints "First message" immediately
C) Does not print anything
D) Throws an error
Answer: C) Does
not print anything.
Explanation:
clearTimeout(timeoutID) cancels the timeout before it can execute the function.
28. How
many times will this code print "Hello"?
javascript
Copy code
let i =
0;
let id =
setInterval(function() {
console.log("Hello");
i++;
if (i >= 3) clearInterval(id);
}, 1000);
A) Once
B) Three times
C) Five times
D) Infinite times
Answer: B) Three
times.
Explanation: The code
uses setInterval() to print "Hello" every second. It stops after
printing three times because clearInterval() is called once i reaches 3.
29. Which
function would you use to execute a function after a delay but only once?
A) setInterval()
B) setTimeout()
C) clearInterval()
D) clearTimeout()
Answer: B)
setTimeout().
Explanation:
setTimeout() is used to execute a function once after a specified delay.
30. What
will the following code do?
javascript
Copy code
let
counter = 0;
let
intervalID = setInterval(function() {
console.log(counter);
counter++;
}, 500);
setTimeout(function()
{
clearInterval(intervalID);
}, 2000);
A) Prints 0, 1, 2, then stops
B) Prints 0, 1, 2, 3, then stops
C) Prints 0, then stops
D) Prints 0, 1, 2, 3 infinitely
Answer: B)
Prints 0, 1, 2, 3, then stops.
Explanation: The
interval prints every 500ms. The clearInterval() call stops it after 2 seconds,
so it prints 0, 1, and 2.
31. How
would you delay a function execution by 500 milliseconds?
A) setTimeout(func, 500)
B) setInterval(func, 500)
C) clearTimeout(func)
D) setTimeout(func)
Answer: A)
setTimeout(func, 500).
Explanation:
setTimeout(func, 500) will delay the function execution by 500 milliseconds.
32. What
will happen if clearInterval() is called twice with the same interval ID?
A) It will throw an error
B) The interval will be cleared once
C) The interval will be cleared twice
D) The interval will not stop
Answer: B) The
interval will be cleared once.
Explanation: Calling
clearInterval() twice with the same ID will have no effect after the first call
because the interval is already cleared.
33. Which
of the following is a correct way to use setInterval()?
A) setInterval(func, 0)
B) setInterval(func)
C) setInterval(func, 1000, 1000)
D) setInterval(func, 1000, 1)
Answer: A)
setInterval(func, 0).
Explanation:
setInterval(func, 0) will execute the function func repeatedly at an interval
of 0 milliseconds (as soon as the event loop allows it).
34. What
will the following code print?
javascript
Copy code
let
counter = 0;
let
intervalID = setInterval(function() {
console.log(counter++);
if (counter === 5) {
clearInterval(intervalID);
}
}, 1000);
A) Prints 0, 1, 2, 3, 4
B) Prints 0, 1, 2, 3, 4, then stops
C) Prints 1, 2, 3, 4, 5
D) Infinite loop
Answer: A)
Prints 0, 1, 2, 3, 4.
Explanation: The
function prints values starting from 0 and stops once counter reaches 5 due to
clearInterval().
35. How
do you execute a function after 2 seconds in JavaScript?
A) setTimeout(func, 2)
B) setTimeout(func, 2000)
C) setInterval(func, 2000)
D) setInterval(func, 2)
Answer: B)
setTimeout(func, 2000).
Explanation:
setTimeout() with 2000 milliseconds (2 seconds) will execute the function after
the specified delay.
36. What
does the setInterval() function return?
A) The interval ID
B) The number of iterations
C) A timeout ID
D) A promise
Answer: A) The
interval ID.
Explanation:
setInterval() returns an ID that can be used to stop the interval later using
clearInterval().
37. What
is the output of this code?
javascript
Copy code
let i =
0;
setInterval(function()
{
console.log(i);
if (i === 5) clearInterval();
i++;
}, 1000);
A) It will print numbers 0, 1, 2,
3, 4, 5 infinitely
B) It will print 0 to 5, then stop
C) It will print numbers 0, 1, 2, 3, 4
D) It will print nothing
Answer: B) It
will print 0 to 5, then stop.
Explanation: The
clearInterval() function is used to stop the interval when i reaches 5.
38. What
will the following code do?
javascript
Copy code
setInterval(function()
{
console.log("Hello World!");
}, 2000);
clearInterval();
A) It will print "Hello
World!" every 2 seconds
B) It will print "Hello World!" immediately
C) It will print "Hello World!" once
D) It will print nothing
Answer: D) It
will print nothing.
Explanation:
clearInterval() stops the interval immediately after being called, so
"Hello World!" will never be printed.
39. How
do you stop a function execution from setTimeout()?
A) clearTimeout()
B) stopTimeout()
C) clearInterval()
D) stopInterval()
Answer: A)
clearTimeout().
Explanation: To stop
a timeout before it executes, use clearTimeout() with the timeout ID returned
by setTimeout().
40. How
can you execute a function in JavaScript after the browser's current event loop
is finished?
A) setTimeout() with a delay of 0
B) setInterval() with a delay of 0
C) clearTimeout() with no delay
D) clearInterval() with no delay
Answer: A)
setTimeout() with a delay of 0.
Explanation:
setTimeout() with a 0 delay executes the function after the current script and
event loop are finished.
41. What
will the following code do?
javascript
Copy code
let
counter = 0;
let
intervalID = setInterval(function() {
if (counter >= 5) {
clearInterval(intervalID);
} else {
console.log(counter);
counter++;
}
}, 1000);
A) Prints 0, 1, 2, 3, 4
B) Prints 0, 1, 2, 3, 4, then stops
C) Prints 0 infinitely
D) Prints nothing
Answer: A)
Prints 0, 1, 2, 3, 4.
Explanation: The code
will print numbers starting from 0 to 4 at 1-second intervals, and then it will
stop after printing 4.
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Timing Events:
42. What will
the following code output?
javascript
Copy code
let timer
= setTimeout(function() {
console.log("Hello");
}, 3000);
clearTimeout(timer);
A) "Hello" will be
printed after 3 seconds
B) "Hello" will be printed immediately
C) Nothing will be printed
D) An error will occur
Answer: C)
Nothing will be printed.
Explanation: The
clearTimeout() function cancels the timeout before it can execute, so no output
occurs.
43. What
happens if clearInterval() is called with an invalid interval ID?
A) The function will throw an
error
B) Nothing will happen
C) The interval will stop
D) The interval will execute once
Answer: B)
Nothing will happen.
Explanation: If
clearInterval() is called with an invalid interval ID, nothing happens, and the
interval continues to run.
44. Which
of the following will execute the function every 1 second indefinitely?
A) setTimeout(func, 1000)
B) setInterval(func, 1000)
C) clearTimeout(func)
D) clearInterval(func)
Answer: B)
setInterval(func, 1000).
Explanation:
setInterval() executes the given function every specified number of
milliseconds indefinitely until stopped.
45. What
will the following code do?
javascript
Copy code
let
counter = 0;
let
intervalID = setInterval(function() {
counter++;
console.log(counter);
if (counter === 3) {
clearInterval(intervalID);
}
}, 2000);
A) It will print 1, 2, 3 and then
stop
B) It will print 1, 2, 3, 4 indefinitely
C) It will print 0, 1, 2, 3 indefinitely
D) It will throw an error
Answer: A) It
will print 1, 2, 3 and then stop.
Explanation: The
interval runs every 2 seconds, printing the counter value and stops when the
counter reaches 3.
46. What
is the purpose of setTimeout() in JavaScript?
A) Executes a function repeatedly
after a delay
B) Executes a function once after a specified delay
C) Clears a set interval
D) Clears a timeout
Answer: B)
Executes a function once after a specified delay.
Explanation:
setTimeout() is used to execute a function only once after a specified delay.
47. What
is the correct syntax to stop an interval in JavaScript?
A) clearTimeout(intervalID)
B) clearInterval(intervalID)
C) stopInterval(intervalID)
D) removeInterval(intervalID)
Answer: B)
clearInterval(intervalID).
Explanation:
clearInterval() is used to stop a recurring interval set by setInterval().
48. Which
of the following is a valid way to set a timeout of 1 second in JavaScript?
A) setTimeout(func, 1000)
B) setTimeout(func, 1)
C) setInterval(func, 1000)
D) setTimeout(func, 100)
Answer: A)
setTimeout(func, 1000).
Explanation:
setTimeout(func, 1000) will call the function after 1 second (1000
milliseconds).
49. How
can you stop a timeout from executing?
A) clearTimeout()
B) clearInterval()
C) stopTimeout()
D) cancelTimeout()
Answer: A)
clearTimeout().
Explanation:
clearTimeout() is used to cancel a timeout that was set by setTimeout() before
it executes.
50. What
will the following code print?
javascript
Copy code
let
counter = 0;
let
interval = setInterval(function() {
counter++;
console.log(counter);
if (counter === 4) clearInterval(interval);
}, 500);
A) 1, 2, 3, 4
B) 1, 2, 3, 4, 5
C) 0, 1, 2, 3, 4
D) 1, 2, 3
Answer: A) 1, 2,
3, 4.
Explanation: The
interval prints the counter value every 500 milliseconds and stops after the
counter reaches 4.
51. How
many times will the following code execute the function?
javascript
Copy code
let
counter = 0;
setInterval(function()
{
counter++;
console.log(counter);
if (counter === 5) {
clearInterval(interval);
}
}, 2000);
A) 5 times
B) 4 times
C) 3 times
D) Infinite times
Answer: A) 5
times.
Explanation: The
setInterval() function will call the function every 2 seconds, and it will stop
after 5 executions when the counter reaches 5.
52. What
will the following code do?
javascript
Copy code
setTimeout(function()
{
console.log("This will run after 3
seconds");
}, 3000);
A) The message will be printed
immediately
B) The message will be printed after 3 seconds
C) The message will be printed after 3 minutes
D) The message will never print
Answer: B) The
message will be printed after 3 seconds.
Explanation:
setTimeout() waits for the specified time (3000 milliseconds or 3 seconds) and
then executes the function.
53. What
happens if clearInterval() is called with an interval ID that does not exist?
A) It will clear all intervals
B) It will throw an error
C) It will have no effect
D) It will stop all time-based events
Answer: C) It
will have no effect.
Explanation: If the
interval ID is invalid, clearInterval() will not do anything.
54. How
can you execute a function in the future with a delay of 0 milliseconds?
A) setInterval(func, 0)
B) setTimeout(func, 0)
C) setTimeout(func, 1)
D) setInterval(func, 1)
Answer: B)
setTimeout(func, 0).
Explanation:
setTimeout(func, 0) will execute the function as soon as possible after the
current event loop finishes.
55. What
is the effect of setInterval() on the function execution time?
A) It executes the function after
a fixed interval time repeatedly
B) It executes the function once after a fixed time
C) It executes the function immediately and stops after one iteration
D) It executes the function in a loop indefinitely
Answer: A) It
executes the function after a fixed interval time repeatedly.
Explanation:
setInterval() will call the specified function repeatedly at the given
interval.
56. What
will the following code output?
javascript
Copy code
let
intervalID = setInterval(function() {
console.log("This message will stop
after 3 iterations");
}, 1000);
setTimeout(function()
{
clearInterval(intervalID);
}, 4000);
A) It will print the message 3
times
B) It will print the message once
C) It will print the message infinitely
D) It will print the message 4 times
Answer: A) It
will print the message 3 times.
Explanation:
setInterval() prints the message every second, and clearInterval() stops it
after 4 seconds (after 3 prints).
57. What
happens when the clearTimeout() function is called without an argument?
A) It cancels all timeouts
B) It cancels the last timeout set
C) It throws an error
D) It does nothing
Answer: D) It
does nothing.
Explanation:
clearTimeout() requires a valid timeout ID, and calling it without an argument
has no effect.
58. How
do you stop a running timeout in JavaScript?
A) Use clearTimeout()
B) Use clearInterval()
C) Use stopTimeout()
D) Use cancelTimeout()
Answer: A) Use
clearTimeout().
Explanation:
clearTimeout() cancels the execution of a timeout before it triggers.
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Timing Events:
59. What
does the following code do?
javascript
Copy code
let
counter = 0;
setInterval(()
=> {
counter++;
console.log(counter);
if (counter === 5) clearInterval(interval);
}, 1000);
A) Prints 1 to 5 every second
B) Prints 1 to 10 every second
C) Prints 5 once
D) Prints 1 every second indefinitely
Answer: A)
Prints 1 to 5 every second.
Explanation:
setInterval() runs the function every second. It prints the counter value until
it reaches 5, at which point clearInterval() stops the interval.
60. Which
method is used to stop an interval from repeating?
A) clearTimeout()
B) clearInterval()
C) clearRepeater()
D) stopInterval()
Answer: B)
clearInterval().
Explanation:
clearInterval() is used to stop an interval set by setInterval().
61. What
is the default behavior of a timeout created with setTimeout()?
A) It runs indefinitely
B) It runs after the specified delay only once
C) It runs repeatedly until stopped
D) It runs every second
Answer: B) It
runs after the specified delay only once.
Explanation:
setTimeout() is used to execute a function once after a specified delay.
62. What
will be the result of this code?
javascript
Copy code
setTimeout(function()
{
console.log("First message");
}, 2000);
setTimeout(function()
{
console.log("Second message");
}, 1000);
A) "First message" is
printed first
B) "Second message" is printed first
C) Both messages are printed at the same time
D) An error will occur
Answer: B)
"Second message" is printed first.
Explanation: The
second setTimeout() has a shorter delay (1 second), so it will execute before
the first one.
63. Which
method can be used to delay the execution of a function?
A) setRepeat()
B) setInterval()
C) setTimeout()
D) clearTimeout()
Answer: C)
setTimeout().
Explanation:
setTimeout() is used to delay the execution of a function by a specified amount
of time.
64. What
happens if you call clearInterval() with an invalid ID?
A) It will stop all intervals
B) It will throw an error
C) It will stop the first interval set
D) Nothing happens
Answer: D)
Nothing happens.
Explanation: If
clearInterval() is called with an invalid ID, it simply does nothing.
65. How
can you execute a function after a delay of 0 milliseconds in JavaScript?
A) setTimeout(func, 0)
B) setInterval(func, 0)
C) setDelay(func, 0)
D) setExecute(func, 0)
Answer: A)
setTimeout(func, 0).
Explanation:
setTimeout(func, 0) executes the function immediately after the current call
stack is cleared.
66. What
is the main difference between setTimeout() and setInterval()?
A) setTimeout() executes once,
while setInterval() executes repeatedly
B) setTimeout() executes repeatedly, while setInterval() executes once
C) setTimeout() has no delay, while setInterval() has a delay
D) Both functions have the same behavior
Answer: A)
setTimeout() executes once, while setInterval() executes repeatedly.
Explanation:
setTimeout() is used to execute a function once after a delay, while
setInterval() runs a function repeatedly at a specified interval.
67. Which
of the following methods is used to stop a timeout?
A) clearTimeout()
B) cancelTimeout()
C) stopTimeout()
D) removeTimeout()
Answer: A)
clearTimeout().
Explanation:
clearTimeout() is used to cancel a timeout that was set with setTimeout().
68. How
long will the following code wait before printing the message?
javascript
Copy code
setTimeout(function()
{
console.log("Delayed Message");
}, 5000);
A) 5 seconds
B) 10 seconds
C) 1 second
D) It prints immediately
Answer: A) 5
seconds.
Explanation: The
message will be printed after 5 seconds because the delay is set to 5000
milliseconds.
69. What
will be the output of the following code?
javascript
Copy code
let
counter = 0;
setInterval(()
=> {
counter++;
if (counter === 4) {
clearInterval(interval);
}
}, 2000);
A) 1, 2, 3, 4 will be printed
every 2 seconds
B) 1, 2, 3 will be printed every 2 seconds
C) 1, 2, 3, 4 will be printed, but after 4 seconds
D) Nothing will print
Answer: B) 1, 2,
3 will be printed every 2 seconds.
Explanation: The
interval runs every 2 seconds and stops after the counter reaches 4.
70. Which
method is used to stop a repeating interval?
A) clearRepeater()
B) clearInterval()
C) stopInterval()
D) cancelInterval()
Answer: B)
clearInterval().
Explanation:
clearInterval() is used to stop a repeating interval set by setInterval().
71. What
will be the result of this code?
javascript
Copy code
let
counter = 0;
let
interval = setInterval(function() {
counter++;
console.log(counter);
if (counter === 3) {
clearInterval(interval);
}
}, 1000);
A) It will print 1, 2, 3 every
second
B) It will print 1, 2, 3 and then stop
C) It will print 1, 2, 3, 4 every second
D) It will print 1, 2, 3 indefinitely
Answer: B) It
will print 1, 2, 3 and then stop.
Explanation: The
setInterval() prints the counter value every second. When the counter reaches
3, clearInterval() stops the interval.
72. What
is the result of the following code?
javascript
Copy code
let
timeout = setTimeout(function() {
console.log("This is delayed");
}, 3000);
clearTimeout(timeout);
A) "This is delayed"
will print after 3 seconds
B) Nothing will print
C) "This is delayed" will print immediately
D) An error will occur
Answer: B)
Nothing will print.
Explanation:
clearTimeout() cancels the timeout before it can execute, so nothing will be
printed.
73. Which
of the following is used to call a function every 2 seconds?
A) setInterval(func, 2000)
B) setTimeout(func, 2000)
C) setDelay(func, 2000)
D) setRepeat(func, 2000)
Answer: A)
setInterval(func, 2000).
Explanation:
setInterval(func, 2000) executes the specified function every 2000 milliseconds
(2 seconds).
74. How
do you execute a function once after a delay of 5 seconds?
A) setTimeout(func, 5000)
B) setInterval(func, 5000)
C) setDelay(func, 5000)
D) setExecute(func, 5000)
Answer: A)
setTimeout(func, 5000).
Explanation:
setTimeout(func, 5000) runs the function once after a 5-second delay.
75. What
happens if you call clearInterval() on an interval that is not set?
A) It will throw an error
B) It will stop all intervals
C) It does nothing
D) It stops the first interval that was set
Answer: C) It
does nothing.
Explanation: If no
interval is set, calling clearInterval() with an invalid ID has no effect.
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76. What
will happen if you use clearInterval() on an interval that hasn't started yet?
A) It will stop the first
interval set
B) It will throw an error
C) It will do nothing
D) It will execute the interval immediately
Answer: C) It
will do nothing.
Explanation: If
clearInterval() is called on an interval that hasn't been started yet (i.e.,
with an invalid or uninitialized ID), it does nothing.
77. Which
of the following JavaScript methods allows you to run a function at regular
intervals?
A) setRepeat()
B) setInterval()
C) setTimeout()
D) setDelay()
Answer: B)
setInterval().
Explanation:
setInterval() is used to execute a function repeatedly at a specified interval.
78. Which
function can be used to stop a timeout?
A) cancelTimeout()
B) clearTimeout()
C) stopTimeout()
D) removeTimeout()
Answer: B)
clearTimeout().
Explanation:
clearTimeout() stops a timeout that was set using setTimeout().
79. What
will the following code output?
javascript
Copy code
let
counter = 0;
let
interval = setInterval(function() {
counter++;
if (counter === 3) {
clearInterval(interval);
}
console.log(counter);
}, 1000);
A) 1, 2, 3
B) 1, 2, 3, 4
C) 1, 2, 3 (then stops)
D) 1, 2, 3 (prints endlessly)
Answer: C) 1, 2,
3 (then stops).
Explanation: The code
prints 1, 2, and 3, and then stops the interval once the counter reaches 3.
80. Which
of the following methods allows for executing a function once after a delay?
A) setTimeout()
B) setInterval()
C) clearTimeout()
D) clearInterval()
Answer: A)
setTimeout().
Explanation:
setTimeout() is used to execute a function once after a specified delay.
81. What
will be the output of this code?
javascript
Copy code
let
timeout = setTimeout(function() {
console.log("This will be displayed
later");
}, 3000);
clearTimeout(timeout);
A) "This will be displayed
later" will appear after 3 seconds
B) Nothing will be printed
C) "This will be displayed later" will appear immediately
D) An error will occur
Answer: B)
Nothing will be printed.
Explanation: The
timeout is cleared immediately, so the function is never executed.
82. What
is the minimum delay possible when using setTimeout()?
A) 0 milliseconds
B) 1 millisecond
C) 10 milliseconds
D) 100 milliseconds
Answer: A) 0
milliseconds.
Explanation: The
minimum delay possible for setTimeout() is 0 milliseconds, though the function
will be executed as soon as the current execution context is completed.
83. Which
of the following is correct about setInterval()?
A) It runs a function once after
a specified delay
B) It runs a function repeatedly at fixed intervals
C) It runs a function repeatedly until stopped
D) Both B and C are correct
Answer: D) Both
B and C are correct.
Explanation:
setInterval() executes a function repeatedly at a fixed interval and can be
stopped using clearInterval().
84. What
will happen if you pass an invalid interval ID to clearInterval()?
A) It will stop all intervals
B) It will throw an error
C) It will stop the first interval that was set
D) Nothing happens
Answer: D)
Nothing happens.
Explanation: Passing
an invalid interval ID to clearInterval() will not stop anything.
85. What
does the following code do?
javascript
Copy code
let count
= 0;
setInterval(()
=> {
count++;
if (count === 5) {
clearInterval(interval);
}
}, 2000);
A) Executes a function every 2
seconds, stops at 5 seconds
B) Executes a function every 2 seconds, stops at 4 seconds
C) Executes the function once at 5 seconds
D) Executes the function indefinitely
Answer: B)
Executes a function every 2 seconds, stops at 4 seconds.
Explanation: The
function will execute every 2 seconds, and will stop once count reaches 5
(after 4 seconds).
86. How
do you stop a repeating function created by setInterval()?
A) cancelInterval()
B) clearInterval()
C) stopInterval()
D) clearFunction()
Answer: B)
clearInterval().
Explanation:
clearInterval() stops the repeating function created by setInterval().
87. Which
of the following statements is true about setTimeout()?
A) It executes a function
immediately
B) It executes a function after a specified delay
C) It executes a function at regular intervals
D) It stops an interval from running
Answer: B) It
executes a function after a specified delay.
Explanation:
setTimeout() delays the execution of a function by a specified time.
88. What
will the following code output?
javascript
Copy code
let
interval = setInterval(function() {
console.log("This runs every
second");
}, 1000);
setTimeout(function()
{
clearInterval(interval);
console.log("Interval cleared");
}, 5000);
A) "This runs every
second" printed indefinitely
B) "This runs every second" printed for 5 seconds, then
"Interval cleared"
C) "Interval cleared" printed immediately
D) Error occurs
Answer: B)
"This runs every second" printed for 5 seconds, then "Interval
cleared".
Explanation: The
message will print every second for 5 seconds and then stop after
clearInterval() is called.
89. What
happens if clearTimeout() is called with an invalid ID?
A) It will stop all timeouts
B) It will stop the first timeout
C) It does nothing
D) It will throw an error
Answer: C) It
does nothing.
Explanation: If the
clearTimeout() is called with an invalid or non-existent ID, it has no effect.
90. What
is the delay time in milliseconds for setTimeout() when the delay is set to 0?
A) 0 milliseconds
B) 10 milliseconds
C) 1 millisecond
D) It executes immediately
Answer: A) 0
milliseconds.
Explanation: A delay
of 0 milliseconds means that the function will execute as soon as the call
stack is clear.
91. What
does the setTimeout() function return?
A) The ID of the set timeout
B) A boolean value indicating success
C) The ID of the function
D) The function itself
Answer: A) The
ID of the set timeout.
Explanation:
setTimeout() returns a unique ID that can be used with clearTimeout() to cancel
the timeout.
92. What
is the main purpose of using setInterval()?
A) To delay the execution of a
function once
B) To stop a function from repeating
C) To repeat a function at regular intervals
D) To execute a function after a specified delay
Answer: C) To
repeat a function at regular intervals.
Explanation:
setInterval() is used to repeat the execution of a function at specified time
intervals.
93. What
will be the output of this code?
javascript
Copy code
let
interval = setInterval(() => {
console.log("Executing...");
}, 1000);
setTimeout(()
=> {
clearInterval(interval);
}, 4000);
A) "Executing..."
printed every second for 4 seconds
B) "Executing..." printed every second indefinitely
C) "Executing..." printed once
D) Nothing printed
Answer: A)
"Executing..." printed every second for 4 seconds.
Explanation: The
setInterval() executes every second, and clearInterval() stops it after 4
seconds.
94. Which
of the following functions runs once after a specified delay?
A) clearTimeout()
B) setInterval()
C) setTimeout()
D) clearInterval()
Answer: C)
setTimeout().
Explanation:
setTimeout() runs a function once after a specified delay.
95. How
can you execute a function repeatedly at fixed intervals?
A) setDelay()
B) setTimeout()
C) setInterval()
D) clearTimeout()
Answer: C)
setInterval().
Explanation:
setInterval() is used to repeatedly execute a function at specified intervals.
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Here are more MCQs related
to JavaScript Timing Events:
96. What
is the default time delay for setTimeout() if no time is specified?
A) 1 millisecond
B) 0 milliseconds
C) 10 milliseconds
D) 100 milliseconds
Answer: B) 0
milliseconds.
Explanation: If no
delay is specified, setTimeout() defaults to a delay of 0 milliseconds, meaning
the function will be executed as soon as the JavaScript engine completes the
current execution cycle.
97. How
can you stop a setInterval() from repeating?
A) Call clearInterval() with the
interval ID
B) Call setTimeout() with a 0 millisecond delay
C) Call clearTimeout() with the timeout ID
D) Both A and B are correct
Answer: A) Call
clearInterval() with the interval ID.
Explanation:
clearInterval() is used to stop a function from repeatedly executing when it is
triggered by setInterval().
98. Which
of the following statements is true for setInterval()?
A) It executes a function only
once after a delay
B) It executes a function repeatedly at fixed intervals
C) It immediately executes a function without any delay
D) It stops executing after the first execution
Answer: B) It
executes a function repeatedly at fixed intervals.
Explanation:
setInterval() runs a function repeatedly, executing it at fixed time intervals.
99. Which
method is used to stop a function set by setTimeout() from executing?
A) clearInterval()
B) stopTimeout()
C) clearTimeout()
D) removeTimeout()
Answer: C)
clearTimeout().
Explanation:
clearTimeout() is used to stop a timeout set by setTimeout() before it
executes.
100. What
will be printed in the console when the following code is executed?
javascript
Copy code
let
counter = 0;
let
interval = setInterval(() => {
counter++;
console.log(counter);
if (counter === 5) {
clearInterval(interval);
}
}, 1000);
A) 1, 2, 3, 4, 5
B) 0, 1, 2, 3, 4, 5
C) 1, 2, 3, 4
D) 5 (prints only once)
Answer: A) 1, 2,
3, 4, 5.
Explanation: The
setInterval() executes every second, printing the counter value. The interval
is cleared once the counter reaches 5.
101. How
do you clear a timeout created by setTimeout()?
A) clearTimeout(timeoutId)
B) stopTimeout(timeoutId)
C) clearInterval(timeoutId)
D) clearStop(timeoutId)
Answer: A)
clearTimeout(timeoutId).
Explanation: The
correct method to stop a timeout is clearTimeout() using the timeout ID
returned by setTimeout().
102.
Which method is used to remove an interval set by setInterval()?
A) stopInterval()
B) clearTimeout()
C) clearInterval()
D) removeInterval()
Answer: C)
clearInterval().
Explanation: The
clearInterval() method is used to stop the repeated execution of a function
created by setInterval().
103. What
happens if you call clearInterval() without passing a valid interval ID?
A) It stops all intervals
B) It throws an error
C) It does nothing
D) It stops the first active interval
Answer: C) It
does nothing.
Explanation: If an
invalid interval ID is passed to clearInterval(), it has no effect, as there is
no active interval to stop.
**104.
How many times will the following code output "Hello"?
javascript
Copy code
let count
= 0;
let
intervalId = setInterval(() => {
console.log("Hello");
count++;
if (count === 3) {
clearInterval(intervalId);
}
}, 1000);
A) 1 time
B) 3 times
C) 5 times
D) Infinite times
Answer: B) 3
times.
Explanation: The
interval will print "Hello" three times and then stop because
clearInterval() is called when count reaches 3.
105.
Which function is used to repeat a block of code continuously until it is
cleared?
A) setRepeat()
B) setTimeout()
C) setInterval()
D) clearTimeout()
Answer: C)
setInterval().
Explanation:
setInterval() is used to execute a block of code repeatedly at specified
intervals until cleared with clearInterval().
106. If
you use setTimeout() with a delay of 0 milliseconds, what happens?
A) The function is executed
immediately
B) The function is executed after 1 millisecond
C) The function is executed after the call stack is cleared
D) The function is never executed
Answer: C) The
function is executed after the call stack is cleared.
Explanation: A
setTimeout() with a delay of 0 milliseconds does not execute immediately. It
waits until the current call stack is completed.
107. What
is the effect of calling clearTimeout() before the timeout function executes?
A) The function executes
immediately
B) The function will not execute
C) The function executes after the timeout
D) The function runs on the next tick
Answer: B) The
function will not execute.
Explanation: Calling
clearTimeout() before the timeout executes will prevent the function from being
called.
108. What
is the return value of setInterval()?
A) A boolean value
B) An integer ID
C) The function itself
D) The timeout value
Answer: B) An
integer ID.
Explanation:
setInterval() returns an integer ID that can be used to clear the interval
later using clearInterval().
109.
Which of the following will execute a function every 2 seconds?
A) setTimeout(myFunction, 2000);
B) setInterval(myFunction, 2000);
C) setDelay(myFunction, 2000);
D) clearInterval(myFunction, 2000);
Answer: B)
setInterval(myFunction, 2000);.
Explanation:
setInterval() is used to execute the function repeatedly every specified time
interval (in this case, 2 seconds).
110. What
happens when clearInterval() is called after an interval is cleared?
A) It clears all intervals
B) It throws an error
C) It has no effect
D) It stops the first interval set
Answer: C) It
has no effect.
Explanation: If an
interval is already cleared or not set, calling clearInterval() does nothing.
111.
Which method is used to stop a repeating function set by setInterval()?
A) clearInterval()
B) removeTimeout()
C) clearTimeout()
D) stopInterval()
Answer: A)
clearInterval().
Explanation:
clearInterval() is used to stop the repeated execution of a function created by
setInterval().
112. How
do you delay the execution of a function in JavaScript?
A) By using setInterval()
B) By using clearTimeout()
C) By using setTimeout()
D) By using clearInterval()
Answer: C) By
using setTimeout().
Explanation:
setTimeout() is used to delay the execution of a function by a specified number
of milliseconds.
113. If a
setTimeout() is called with a delay of 0 milliseconds, when will the function
execute?
A) Immediately
B) After the current event is complete
C) After 1 second
D) After the page loads
Answer: B) After
the current event is complete.
Explanation:
setTimeout() with a delay of 0 milliseconds doesn't execute immediately. It
waits until the current task is completed and the call stack is cleared.
