JSON.stringify 와 재귀를 이용한 과제

function stringifyJSON(obj) {
  // your code goes here
  if(typeof obj === 'number'){
    return String(obj);
  } else if(obj === null ){
    return `${obj}`
  }else if(typeof obj === 'string'){
    return `"${obj}"`
  }

  let result = ""
  if(Array.isArray(obj)){
    result += "[";
    for(let el of obj){
        result += `${stringifyJSON(el)},`;
    }
    if(result === "["){
      return result+"]"
    }else{
      return result = result.slice(0, result.length-1) + "]"
    }
  }else if(typeof obj === "object"){
    result += "{"
    for(let key in obj){
        if(obj[key] === undefined || typeof obj[key] === 'function'){
          continue;
        }
        result += `"${key}":`
        result += `${stringifyJSON(obj[key])},`;
    }
    if(result === "{"){
      return result+"}"
    }else{
      return result = result.slice(0, result.length-1) + "}"
    }
  }return String(obj);
};