Đặng Đình Sáng

Posted on Jul 1, 2024

Javascript Quizzes You Can't Solve

Đặng Đình Sáng · 2024-07-01T02:53:04Z

Q1 console . log ( 018 - 015 ); console . log ( " 018 " - " 015 " ); Enter fullscreen mode Exit fullscreen mode Q2 const isTrue = true == []; const isFalse = true == ! []; console . log ( isTrue + isFalse ); Enter fullscreen mode Exit fullscreen mode Q3 console . log ( 3 > 2 > 1 ); Enter fullscreen mode Exit fullscreen mode Q4 console . log ( typeof typeof 1 ); Enter fullscreen mode Exit fullscreen mode Q5 console . log (( ' b ' + ' a ' + + ' a ' + ' a ' ). toLowerCase ()); Enter fullscreen mode Exit fullscreen mode Q6 console . log ( typeof NaN ); Enter fullscreen mode Exit fullscreen mode Q7 console . log ( 0.1 + 0.2 == 0.3 ); Enter fullscreen mode Exit fullscreen mode Q8 const numbers = [ 33 , 2 , 8 ]; numbers . sort (); console . log ( numbers [ 1 ]) Enter fullscreen mode Exit fullscreen mode Conclusion What percentage of the eight questions were correct? If you get all of them right, please leave a comment! Ref Javascript quizz The original article

#javascript #webdev #learning

Q1

console.log(018 - 015);
console.log("018" - "015");

Q2

const isTrue = true == []; 
const isFalse = true == ![]; 

console.log ( isTrue + isFalse);

Q3

console.log(3 > 2 > 1);

Q4

console.log(typeof typeof 1);

Q5

console.log(('b' + 'a' + + 'a' + 'a').toLowerCase());

Q6

console.log(typeof NaN);

Q7

console.log(0.1 + 0.2 == 0.3);

Q8

const numbers = [33, 2, 8];
numbers.sort();
console.log(numbers[1])

Conclusion

What percentage of the eight questions were correct?
If you get all of them right, please leave a comment!

Ref

Top comments (4)

Jaydeep Pipaliya • Jul 1 '24 • Edited

018 is treated as a decimal (18) since it is not a valid octal number, while 015 is a valid octal (13). So, 18 - 13 = 5.
"018" and "015" are converted to numbers 18 and 15. So, 18 - 15 = 3.

true == [] converts to 1 == 0, which is false. So, isTrue is false..
true == ![] converts to true == false (1 == 0), which is false. So, isFalse is false.
false + false is 0 + 0, which equals 0. So, console.log(isTrue + isFalse); will log 0.

This will log false. Here's why:

First, 3 > 2 evaluates to true.
Then, true > 1 is evaluated. In JavaScript, true is converted to 1, so 1 > 1 evaluates to false.

A4
This will log "string". Here's why:

typeof 1 returns "number".
typeof "number" returns "string".

This will log "banana". Here's why:

'b' + 'a' is 'ba'.
+ 'a' is NaN because 'a' cannot be converted to a number.
'ba' + NaN + 'a' results in 'baNaNa'.
Calling .toLowerCase() on 'baNaNa' gives 'banana'.

This will log "number". NaN (Not-a-Number) is of type number in JavaScript.

This will log false. Due to floating-point precision issues, 0.1 + 0.2 does not exactly equal 0.3. Instead, it equals 0.30000000000000004.

This will log 33. The sort() method sorts the array elements as strings by default. Hence, the array becomes [2, 33, 8].

Đặng Đình Sáng • Jul 1 '24

@itsjp

A1

An octal number is a number in JavaScript that has a leading zero.
018 is regarded as a decimal number, nevertheless, because it is an incorrect octal number. 015 is 13 in octal notation. 018-015 = 18-13 = 5 as a result.

A2

To begin with, allow me to clarify the first line: true and [] are changed to integers because they are of different kinds. First to be evaluated are number(true) and number([]), which are 1 and 0, respectively. const isTrue = false since 1 == 0.

Although true and ![] are both boolean values and are not converted to integers, it appears that the second line is the same. Additionally, ![] would be false because [] is understood to be true.
const isFalse = false and const isFalse = true are the results.

The final line, console.log (isTrue + isFalse); becomes console.log (false + false); as a result of the foregoing. console.log (0 + 0); becomes a number instead than false.
Therefore, the solution is 0.

Jaydeep Pipaliya • Jul 2 '24

thank you for the corrections

Syed Muhammad Ali Raza • Jul 1 '24

😔