Quato.js

// naive solution
const balancedBrackets = function (str) {
  const stack = [];
  const opener = '(';
  const closer = ')';

  for (let i = 0; i < str.length; i++) {
    if (str[i] === opener) {
      stack.push(str[i]);
    } else if (str[i] === closer) {
      const top = stack.pop();
      if (top !== opener) {
        return false;
      }
    }
  }

  return stack.length === 0;
};

// Advanced solution
const balancedBrackets = function (str) {
  const stack = [];
  const opener = {
    '{': '}',
    '[': ']',
    '(': ')',
  };
  const closer = '}])';

  for (let i = 0; i < str.length; i++) {
    if (str[i] in opener) {
      stack.push(str[i]);
    } else if (closer.includes(str[i])) {
      const top = stack.pop();
      const pair = opener[top];
      if (pair !== str[i]) {
        return false;
      }
    }
  }

  return stack.length === 0;
};