Close Parentheses codewars simple string indices

solution.js

// https://www.codewars.com/kata/simple-string-indices

function closeParens(str, openParenIndex) {
  let gate = 1;
  let closeParenIndex = -1;
  
  for(let i = openParenIndex + 1; i <= str.length; i++) {
    
    if(str[openParenIndex] != "(") {
      return closeParenIndex;
    } else if(str[i] === "(") {
      ++gate;
      
    } else if(str[i] === ")") {
      --gate;
      if(gate === 0) {
        closeParenIndex = i;
      }
    }
  }
  return closeParenIndex;
}