function isLeft(char) {
 return (char === "(" || char === "[" || char === "{") ? true : false;
}

function isValidPair(str) {
  str.split("");
  var stack =[];
  var pairs = {")": "(", "]": "[", "}": "{"};

  if (str.length <= 1) {
    return false;
  }

  for (var i =0; i < str.length; i++) {
    if (isLeft(str[i])) {
      stack.push(str[i]);
    } else {
      if (pairs[str[i]] === stack[stack.length -1]) {
        stack.pop();
      } else {
        return false;
      }
    }
  }

  if (stack.length !== 0) {
    return false;
  }

  return true;
}


console.log(isValidPair("()[{}]"));
console.log(isValidPair("{[}]"));
console.log(isValidPair("{()"));
console.log(isValidPair("{("));