Console methods beyond log in Node.js - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of console.count usage

What will be printed to the console after running this Node.js code snippet?

Node.js

console.count('label');
console.count('label');
console.count('other');
console.count('label');

A

label: 1
label: 2
other: 1
label: 3

B

label: 1
label: 1
other: 1
label: 1

C

label: 1
label: 2
other: 2
label: 3

D

label: 0
label: 1
other: 0
label: 2

💡 Hint

console.count keeps track of how many times a label has been counted.

The console.count method prints the label followed by the number of times it has been called with that label. Each call increments the count for that label.

❓ Predict Output

intermediate

Behavior of console.assert with false condition

What will be the output when running this Node.js code?

Node.js

console.assert(false, 'Assertion failed!');
console.assert(true, 'This will not show');

A Assertion failed!

B No output

C Error: Assertion failed!

D

Assertion failed!
This will not show

💡 Hint

console.assert only prints the message if the first argument is false.

console.assert prints the message only if the condition is false. It does not throw an error, just logs the message.

❓ Predict Output

advanced

Output of console.group and console.groupEnd

What will be the console output of this Node.js code snippet?

Node.js

console.log('Start');
console.group('Group 1');
console.log('Inside group');
console.groupEnd('Group 1');
console.log('End');

A

Start
Group 1
Inside group
End

B

Start
  Group 1
  Inside group
End

C

Start
Inside group
End

D

Start
Group 1
  Inside group
End

💡 Hint

console.group indents the following logs until console.groupEnd is called.

console.group indents the output of subsequent logs until console.groupEnd is called. The group label itself is printed without indentation.

❓ Predict Output

advanced

Effect of console.time and console.timeEnd

What will this Node.js code print to the console?

Node.js

console.time('timer');
setTimeout(() => {
  console.timeEnd('timer');
}, 100);

A timer: 100ms

B timer: <some number close to 100>ms

C timer: 0ms

D Error: No such label 'timer'

💡 Hint

console.timeEnd prints the elapsed time since console.time was called with the same label.

console.time starts a timer with a label. console.timeEnd stops the timer and prints the elapsed time. The time will be close to the delay in setTimeout.

❓ lifecycle

expert

Understanding console.trace output

What does the following Node.js code output when executed?

Node.js

function a() {
  b();
}
function b() {
  c();
}
function c() {
  console.trace('Trace here');
}
a();

A

Trace here
    at c (<anonymous>)

B

Trace here
    at a (<anonymous>)
    at b (<anonymous>)
    at c (<anonymous>)

C

Trace here
    at c (<anonymous>)
    at b (<anonymous>)
    at a (<anonymous>)
    at <anonymous>

D

Trace here
    at b (<anonymous>)
    at c (<anonymous>)
    at a (<anonymous>)

💡 Hint

console.trace prints the call stack from the point it is called.

console.trace prints the message and the full call stack showing the order of function calls leading to it, starting from the current function back to the entry point.