Lend transactions balances out to zero

function check(transactions) {
    var balance = 0; // start with a zero balance
    var result = []; // start with an empty array
    for (var i = 0; i < transactions.length; i++) {
        var transaction = transactions[i]; // get the current transaction
        if (transaction[0] === 'Lend') { // if it's a lend
            balance += transaction[1]; // add the amount to the balance
        } else { // otherwise it's a borrow
            balance -= transaction[1]; // subtract the amount from the balance
        }
        if (balance === 0) { // if the balance is zero
            result.push(transaction); // add the transaction to the result
        }
    }
    return result;
}