javascript balance parentheses

balance.js

function balanceA(arr) {

  var filtered = arr.filter(function(item) {
    return item.match(/(\(|\))/g)
  });
  
  function test(a) {

    // these conditions are insane, there must be a far easier way of doing this...

    if (a.length == 0) {
      return true;
    }

    else if (a.length % 2 !== 0) {
      return false;
    }
    // last two are ')(' and length is greater than 2
    else if ((a[a.length-2] == ")" && a[a.length-1] == "(") && a.length > 2 ) {
      return false;
    } 

    // first two are "()" - remove them and recurse
    else if ((a[0] == "(" && a[1] == ")")) {
      return test(a.slice(2)); 
    }

    // last two are "()" - remove them and recurse
    else if (a[a.length-1] == ")" && a[a.length-2] == "(") {
      return test(a.slice(0,-2)); 
    }

    // first two are ')(' and length is greater than 2
    else if ((a[0] == ")" && a[1] == "(") && a.length > 2 ) {
      return false;
    }

    // first is "(", last is ")" - remove them and recurse
    else if (a[0] == "(" && a.last() == ")")  {
        return test(a.slice(1, -1));
    }

    // it must be ')(', and that's ok, because it survived previous conditions
    else {
      return true;
    }

  }

  return test(filtered);

}

function balanceB(arr, unbalancedParentheses) {
    var first = arr[0];
    unbalancedParentheses = unbalancedParentheses || 0;
    if (first == '(') 
      unbalancedParentheses++;
    else if (first == ')') 
      unbalancedParentheses--;
    if (unbalancedParentheses < 0) 
      return false;
    if (arr.length == 1) 
      return unbalancedParentheses == 0;
    return balanceB(arr.slice(1), unbalancedParentheses);
}

console.log("true...");
console.log(balanceA("(if (zero? x) max (/ 1 x))".split("")));
console.log(balanceA("I told him (that it’s not (yet) done). (But he wasn’t listening)".split("")));
console.log(balanceA("(())()".split("")));
console.log(balanceA("(())(())".split("")));
console.log(balanceA("(()()())".split("")));
console.log(balanceA("(((()())))".split("")));
console.log(balanceA("(()((()())))".split("")));
console.log(balanceB("(if (zero? x) max (/ 1 x))".split("")));
console.log(balanceB("I told him (that it’s not (yet) done). (But he wasn’t listening)".split("")));
console.log(balanceB("(())()".split("")));
console.log(balanceB("(())(())".split("")));
console.log(balanceB("(()()())".split("")));
console.log(balanceB("(((()())))".split("")));
console.log(balanceB("(()((()())))".split("")));

console.log("false...");
console.log(balanceA(":-)".split("")));
console.log(balanceA("())(".split("")));
console.log(balanceA("(()())((()()))))".split(""))); 
console.log(balanceB(":-)".split("")));
console.log(balanceB("())(".split("")));
console.log(balanceB("(()())((()()))))".split(""))); 

return test(y, lastAtTheFrontWasClosed, lastAtTheEndWasClosed);

function balance(arr, closeparens) {
var tail = arr.slice(1),
next = arr[0];
closeparens = closeparens || 0;

if (next == '(') {
closeparens++;
} else if (next == ')') {
closeparens--;
}

if (closeparens < 0) {
return false;
}

if (arr.length == 1) {
return closeparens == 0;
}

return balance(tail, closeparens);
}

rename 'closeparens' to 'unbalancedParentheses'