In node.js below code showing the error when i try to assign the variable true or false then and also a error when i try to update the one field then

In this below code i have a variable matchData this variable i starting assign the false then
i show my data in else condition after that matchData=true but when i check the variable is matchData true or false then showing the false again an again... also see the comment line its also important when if the matchdata===true after then how can i update the particular filed soo also check this

const a = [
{
  Topic: "TRACK",
  SID: "1",
  GPSlat: "4322",
  GPSlong: "104014684",
  GPSat: "43788",
  GPSspd: "20",
  GPShead: "29499222",
  GPSepoch: "1638451313",
  id:"3q6yxhBxnxVEtyZcAtNX"
}
]



const b = [
  {
  Topic: "TRACK",
  SID: "1",
  GPSlat: "4322",
  GPSlong: "104014684",
  GPSat: "43788",
  GPSspd: "20",
  GPShead: "29499222",
  GPSepoch: "1638451323"
},
  {
  Topic: "TRACK",
  SID: "1",
  GPSlat: "4322",
  GPSlong: "104014684",
  GPSat: "43788",
  GPSspd: "20",
  GPShead: "29499222",
  GPSepoch: "1638451333"
}
]


    //--------------------THis is for SID ---------------------------------------
    var result = a.filter(o => !b.some(v => v.SID === o.SID)); //

    //--------------------THis is for GPSlat ---------------------------------------
    var result1 = a.filter(o => !b.some(v => v.GPSlat.substr(0, 4) === o.GPSlat.substr(0, 4)));

    //--------------------THis is for GPSlong ---------------------------------------
    var result2 = a.filter(o => !b.some(v => v.GPSlong.substr(0, 4) === o.GPSlong.substr(0, 4)))
    var DateTime = a.GpSepoch;
    //--------------------This is for date and time -----------------------------------
    var result3 = a.filter(o => !b.some(v => v.GPSepoch === o.GPSepoch))
    
    var matchData=false;
    
      if (result.length === 0) {
        
        if (result1.length === 0) {
            
            if (result2.length === 0) {
                 
                if (result3.length === 0 || matchData=== true)
                {
                    //how can i update this particular result3 data here using id alse soo please check the error and showing whats the right way to update the particular field
                     this.db.collection(`DevicesData/`).update({'payload.GPSepoch':DateTime}).catch(error =>{
                        console.log(error,"Error");
                    });
                    console.log("hereeeeeee")
                    
                }
                else
                {
                    console.log(result3,"GPSepoch")
                    matchData=true;
                    
                }
            }
            else
            {
                
                console.log(result2,"GPSlong")
                
            }
        }
        else
        {
            console.log(result1,"GPSlat")
            
        }
      }
      else{
          console.log(result,"SID")
      }
 

thank you