Algorithm: optimizing 'balancing brackets'

Question

I have been posed the following question...

Given a N different open and close braces in a string "( { [ } ] )", check whether the string has matching braces. Return true if the braces match, false otherwise.

Here is the answer I came up with...

function braceeql(braces){
  var leftpar = 0; 
  var rightpar = 0; 
  var leftbrace = 0;
  var rightbrace = 0;
  var leftcurl = 0;
  var rightcurl = 0;

  for(var index = 0; index < braces.length; index++){
    if(braces[index] == ')'){
      leftpar += 1;
    }else if(braces[index] == '('){
      rightpar += 1;
    }else if(braces[index] == '['){
      leftbrace += 1;
    }else if(braces[index] == ']'){
      rightbrace += 1;
    }else if(braces[index] == '{'){
      leftcurl += 1;
    }else if(braces[index] == '}'){
      rightcurl += 1;
    }
  }
  if(leftcurl == rightcurl && leftbrace == rightbrace && leftpar == rightpar){
    console.log(true)
  }else{
    console.log(false)
  }
}

This is really meaty piece of code, but it sure as heck works. I am seeing differing opinions about how others attacked this problem, but am left wondering is there a better/cleaner way of solving this algorithm without compromising the big O?

I am very open to suggestions and other ways of looking at this problem.

Answer 1

Using Stack

The following solution has time complexity of O(n)

function isBalanced(str) {
  const map = {
    '(': ')',
    '[': ']',
    '{': '}',
  };
  const closing = Object.values(map);
  const stack = [];
        
  for (let char of str) {
    if (map[char]) {
      stack.push(char);
    } else if (closing.includes(char) && char !== map[stack.pop()]) {
      return false;
    }
  }
  return !stack.length;
}