i wanted to use true or false on my code but didnt know how to proceed.

i will never understand java

A lot of solutions with var are from before let and const were released in JavaScript. I wholeheartedly agree though!

in reduce the two param is the defulat number
i think you donot add 0

I would recommend using 'const', or if not possible 'let' instead of 'var'. just for scope reasons as best practice

another clever person

такое решение не проходит проверку в случае аргумента array=[88,19,32,75,74,66,98,56,65,67,68,48]. Среднее для такого массива будет 63, а решение в одну строчку дает результат 62,99999999999.

simple and clear solution in one line

neat