Not fully working code

.js

const operations = {
"+": (num1, num2) => num1+num2,
"-":(num1, num2) => num1 - num2,
"*": (num1, num2) => num1*num2,
"/": (num1, num2) => num1/num2,
}
const parseString = str => {
	const resultArr = []
   	let parentesisBuffer = [];
    let parentesisBufferActive = false
  str.split("").forEach((symbol) => {
  			if(symbol === " "){return}
        if(symbol === "("){
          parentesisBufferActive =true
          return
        }
        if(parentesisBufferActive) {
          if(symbol === ")"){
            parentesisBufferActive = false
            resultArr.push(parentesisBuffer)
            parentesisBuffer = []
            return
          } else {
            parentesisBuffer.push(symbol)
          }
        } else {
            resultArr.push(symbol)
        }
  })
  return resultArr
}

const calculate = (parsedStr) => {
	let opsFunc = operations["+"];
	return parsedStr.reduce((acc, el) => {
  	if(!isNaN(Number(el))) {
  	      return opsFunc(acc,Number(el))
  	    } else if(Object.keys(operations).includes(el)){
     opsFunc = operations[el]
     return acc
    } else if(Array.isArray(el)) {
    	return opsFunc(calculate(el), acc)
    } else {
    	throw "unexpected character"
    }
    return acc
  }, 0)
}

const getResult=(str) => calculate(parseString(str))

let res = calculate(parseString("1+(3+4*2)-1"))