balanced brackets

index.js

const OPEN_SYMBOLS = ['{', '[', '('];
const CLOSE_SYMBOLS = {
   ')': '(',
   ']': '[',
   '}': '{' 
};

function isBalanced(s) {
    const heap = [];
    
    for(let i = 0; i < s.length; i++) {
        const symbol = s[i];
        
        if(OPEN_SYMBOLS.includes(symbol)) {
            // push to heap
            heap.push(symbol);
        } else {
            if(heap[heap.length - 1] === CLOSE_SYMBOLS[symbol]) {
                // if match, pop the open symbol from heap
                heap.pop();
            } else {
                return 'NO';
            }
        }
    }
    
    return heap.length === 0 ? 'YES' : 'NO';
}