My advice is to look into 'type coercion' and while you're at it, 'type conversion' and figure out the difference. It's quite interesting stuff.

how and why does this work ?

why though ?

I guess because of the readability (altho I've done pretty much the same thing xD)

how is it faster ?

yooo comparing string letters is wild. How do you even find out you can do that ?!

can you expanciate please ? also what is the problem with modifying the value of sign ?

please can you explain more about this? and what would be the most performant solution in your opinion ?

so simple yet i could not think of it

i completly forgot about "toString" and used the loop to split the number before using reduce, this is outrageous