However, x.length === o.length it doesn't work for me. Maybe you meant x?.length === o?.length

You must also aware of how in operator works because it is not only work on its parent object it is also works on object prototype chaining so let's say that property name already exists in object prototype then it will generate bug to your code

You can make your code shorter by using template literals instead of concatenating it with + operator

because of this code i now understand what this codes do unlike from the first one it is readable for beginners like me

this is better practice because in real life cases you might wanna change the letter "r" into something else...
and in his solution just changing the letter "r" will do it...

I wonder why this code becomes best practices and clever!

Its nice because it is a short code but next time you should avoid ternary operator with more than one condition

You need to put a simple checking here if it is equal to zero then return the number if its not give its opposite number

This solution will work but if you leave the parameter as empty it will return false but i considered that the input should be boolean so its not a big deal tho

you can skip the if else statement just return the value but if you are beginner and dont know much about ternary operator then go for it

i really like this solution when it comes to checking if its even or odd because it is more readable and maintainable