I'm perplexed about the logic behind this function potentially returning true. My understanding is that if an item is added to the stack, then evaluating !stack.length would yield false, correct? It seems like there might be a gap in my knowledge regarding how stacks operate, as I can't seem to pinpoint where I've gone wrong.
var isValid = function (s) {
const hash = {
'(': ')',
'{': '}',
'[': ']',
};
const stack = [];
for (const char of s) {
if (char in hash) stack.push(char);
else {
const top = stack.pop();
if (top === undefined || hash[top] !== char) {
return false;
}
}
}
return !stack.length;
};