Is matching brackets

isMatchingBrackets.js

function isMatchingBrackets(str) {
    let stack = [];
    const map = {
        '(': ')',
        '[': ']',
        '{': '}'
    };
    let answer = false;

    for (let c of [...str]) {
        if (Object.keys(map).includes(c)) {
            // is opening
            stack.push(c);
        } else {
            // if it's closing type
            // check if stack is empty
            if (stack.length === 0) {
                // i return false because stack is empty and i want to break out of the loop
                answer = false
                break;
            } else {
                const lastOpen = stack.pop() // has to be  ( { [
                const match = map[lastOpen] === c;
                if (match) {
                    // i have a match (this closing has an opening as the last item in stack
                    answer =  true;
                } else {
                    // i dont have a match
                    answer = false;
                }
            }
        }
    }
    if (stack.length) {
        answer = false
    }
    return answer;
}