/**
 * @param {string} s
 * @return {boolean}
 */
var isValid = s => {
  const par = {
      "(": ")",
      "{": "}",
      "[": "]",
    };
  const rep = [];
  return [...s].every(x => par[x]
                      ? rep.push(par[x])
                      : rep.pop() === x) && !rep.length;
};

/**
 * @param {string} s
 * @return {boolean}
 */
var isValid2 = s => {
  const par = {
      "(": ")",
      "{": "}",
      "[": "]",
    };
  const rep = [];
  for (let i = 0; i < s.length; i++) {
    if (par[s[i]]) {
      rep.push(par[s[i]]);
    } else {
      if (rep.pop() !== s[i]) {
        return false;
      }
    }
  }
  return rep.length === 0;
};