我下面的函数读取accounts.csv，但是，我希望能够在其中写入。每次我执行fs.createWriteStream操作时，它都会覆盖整个文件并替换它。这是我的代码。我要追加结果

let stream = fs.createReadStream("accounts.csv");

fast
    .fromStream(stream, {headers : ["Account",
        "OrgName", "Contact1", "Contact2", "AddrLine1",
        "AddrLine2", "City", "State", "ZipPostal", "Country",
        "AccountType", "ACCTTYPE", "Partner", "PTRDATE", "LSTCONTD",
        "LSTGIFTDT", "LSTGIFTAmt"]})
    .on("data", function(data){
      var orgName = data
      console.log(data);
    })
    .on("end", function(){
      console.log("done");
    });

let ws = fs.createWriteStream('accounts.csv');

fast.
    write([

        {r: "r1", s:"s1"}

    ], {headers:true})
        .pipe(ws);