Zero Balanced Array

zero-balanced.js

/*
* An array is called zero-balanced if its elements sum to 0 and for each positive element n, 
* there exists another element that is the negative of n. Write a function named ìsZeroBalanced that returns true 
* if its argument is zero-balanced array, else return false. Note that an empty array will not sum to zero.
*/

function isZeroBalanced(a){
  return a.length > 0 && a.every(x => a.includes(-x)) && a.reduce((acc, x) => acc + x) === 0
}