a,b,c,d
1,2,3,4
5,6,7,8
...

[
{"a": 1,"b": 2,"c": 3,"d": 4},
{"a": 5,"b": 6,"c": 7,"d": 8},
...
]

var es = require('event-stream')
    es.pipeline(                         //connect streams together with `pipe`
      process.openStdin(),              //open stdin
      es.split(),                       //split stream to break on newlines
      es.map(function (data, callback) { //turn this async function into a stream
        callback(null
          , JSON.stringify(parseCSVLine(data)))  // deal with one line of CSV data
      }),
      process.stdout
      )

var Converter=require("csvtojson").core.Converter;

var csvConverter=new Converter(false); // The parameter false will turn off final result construction. It can avoid huge memory consumption while parsing. The trade off is final result will not be populated to end_parsed event.

var readStream=require("fs").createReadStream("inputData.csv");

var writeStream=require("fs").createWriteStream("outpuData.json");

var started=false;
csvConverter.on("record_parsed",function(rowJSON){
    if (started){
        writeStream.write(",n");
    }
    writeStream.write(JSON.stringify(rowJSON));  //write parsed JSON object one by one.
    if (started==false){
        started=true;
    }
});

writeStream.write("[n"); //write array symbol

csvConverter.on("end_parsed",function(){
    writeStream.write("n]"); //end array symbol
});

csvConverter.from(readStream);

csvtojson myCSVFile.csv