Using reduce to balance parentheses.js

//Returns 0 if balanced.
const isParensBalanced = (str) => {
  return str.split('').reduce((counter, char) => {
    if(counter < 0) { //matched ")" before "("
      return counter;
    } else if(char === '(') {
      return ++counter;
    } else if(char === ')') {
      return --counter;
    }  else { //matched some other char
      return counter;
    }
    
  }, 0); //<-- starting value of the counter
}

isParensBalanced('(())') // 0 <-- balanced
isParensBalanced('(asdfds)') //0 <-- balanced

isParensBalanced('(()') // 1 <-- not balanced
isParensBalanced(')(') // -1 <-- not balanced