如何逐个将json数据添加到csv文件中？

我需要从开始到结束开始将json数据添加到csv文件。但每一行都会每分钟添加一行。在我的情况下，它在第一分钟就添加了所有这些内容。这是我的代码。

var unirest = require('unirest');
var fs = require('fs');
var outFilename = 'mert_akel_minutereadings.csv';

var interval = setInterval(function () { post(); }, 60000); //Write to file every minute

function post(){
    unirest.post('')
    .headers({'Accept': 'application/json', 'appKey': 'XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX'})
    .end(function (response) {
      writeToCsv(response.body);
    });
}


function writeToCsv(inJSON){    

        var outCSV = inJSON.rows;

    //  console.log(outCSV)

        var csv = [];

        for(var k in outCSV) {
            var items = [[outCSV[k].PowerPlant , outCSV[k].gen1min , outCSV[k].gen1minDateTime, timeConverter(outCSV[k].gen1minDateTime)]];
             for (index = 0; index < items.length; ++index) {
                csv.push(items[index].join(', ') + '\n');
             }

             fs.writeFile(outFilename, csv, function (err) {
                if (err) {
                    return console.log(err);
                }

                console.log("Added one row!")

             });
        }

    }

function timeConverter(UNIX_timestamp){
             var a = new Date(UNIX_timestamp*1000);
             var hour = a.getUTCHours();
             var min = a.getUTCMinutes();
             var sec = a.getUTCSeconds();
             var time = hour+':'+min+':'+sec ;
             return time;
    }

如果有人可以提供帮助，我将不胜感激。