Serialize and Flatting object data into string

gistfile1.txt

const findObjectDataRecursive = function (obj, subKey='') {
                    let dataArray = []; 
                    if (typeof (obj) === "undefined" || obj === null)
                        return undefined;
                    
                    if (typeof obj === "object"){
                        let result = [];
                        if (Array.isArray(obj)){
                            for(let i = 0; i < obj.length; i++) {
                                let x = findObjectDataRecursive(obj[i], subKey + '['+i+']');
                                if (typeof x !== "undefined"){
                                    for (const e of x) {
                                      result.push(e);
                                    }
                                }
                            }
                        } else {
                            for (const objKey in obj) {
                              if (obj.hasOwnProperty(objKey)){
                                  let key = subKey!=null && subKey!==""? subKey + '['+objKey+']' : objKey;
                                  let x = findObjectDataRecursive(obj[objKey], key);
                                  if (typeof x !== "undefined"){
                                      for (const e of x) {
                                        result.push(e);
                                      }
                                  }
                              }
                            }
                        }
                        
                        for (const resultKey of result) {
                          dataArray.push(resultKey);
                        }
                    }
                    else{
                        dataArray.push(subKey + '=' + encodeURIComponent(obj));
                    }
                    return dataArray;
                };
                
                const serialize = function (obj) {
                    let data = findObjectDataRecursive(obj);
                    let str = "";
                    let i = 0;
                    do {
                        str += data[i++];
                    } while(i<data.length && (str+="&"));
                    
                    return str;
                }
                
                const filterUrl = serialize(filters);