Recursive setTimeout vs setInterval in Node.js - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to schedule a function to run repeatedly using setInterval.

Node.js

setInterval(() => {
  console.log('Hello every second');
}, [1]);

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

A1000

B5000

C10

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using 100 instead of 1000 causes the function to run every 0.1 seconds.

Using 5000 runs the function every 5 seconds, which is slower than intended.

The setInterval function takes the delay in milliseconds as the second argument. To run every second, use 1000 ms.

2fill in blank

medium

Complete the code to create a recursive setTimeout that logs 'Tick' every 2 seconds.

Node.js

function tick() {
  console.log('Tick');
  setTimeout(tick, [1]);
}
tick();

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

A500

B1000

C2000

D3000

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1000 causes the function to run every 1 second instead of 2.

Using 3000 causes the function to run every 3 seconds, which is slower.

The recursive setTimeout calls itself after the delay. To run every 2 seconds, use 2000 ms.

3fill in blank

hard

Fix the error in the recursive setTimeout code to avoid multiple overlapping calls.

Node.js

function repeat() {
  console.log('Running');
  [1](() => {
    repeat();
  }, 1000);
}
repeat();

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AsetInterval

BsetTimeout

CclearTimeout

DclearInterval

Attempts:

3 left

💡 Hint

Common Mistakes

Using setInterval causes the function to run repeatedly without waiting for the previous call to finish.

Using clearTimeout or clearInterval here is incorrect because they cancel timers.

Using setTimeout recursively schedules the next call after the current one finishes, avoiding overlaps.

4fill in blank

hard

Fill both blanks to create a recursive setTimeout that stops after 5 runs.

Node.js

let count = 0;
function run() {
  if (count [1] 5) {
    console.log('Run number', count);
    count++;
    setTimeout(run, [2]);
  }
}
run();

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

A<

B<=

C1000

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using <= 5 causes the function to run 6 times instead of 5.

Using 500 ms delay runs the function twice as fast as intended.

The condition count < 5 stops after 5 runs. The delay 1000 ms makes it run every second.

5fill in blank

hard

Fill all three blanks to create a recursive setTimeout that counts down from 3 and then stops.

Node.js

let num = 3;
function countdown() {
  if (num [1] 0) {
    console.log(num);
    num [2] 1;
    setTimeout(countdown, [3]);
  } else {
    console.log('Done!');
  }
}
countdown();

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

A>

B-=

C1000

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using < 0 causes the countdown to never stop.

Using += 1 increases num and causes an infinite loop.

Using delay other than 1000 changes the timing.

The countdown stops when num > 0 is false. The -= 1 decreases the number by one each time. The delay 1000 ms makes it run every second.