nodejs多个目录文件合并成一个

var fs = require('fs');
var baseUrl = './data';
var createJson = './data.json';
fs.readdir(baseUrl, function(err, files) {
        if (err) {
            throw err;
        }
        var filePath = '';

        var fileReadStream;
        var fileWriteStream = fs.createWriteStream(createJson);


        createStramFile();
        var fileNum = files.length-1;

        function createStramFile(){
            var currentfile = baseUrl+'/' + files.shift();
            fileReadStream = fs.createReadStream(currentfile);
            fileReadStream.pipe(fileWriteStream,{end:false});
            fileReadStream.on("end", function() {
                console.log(currentfile + ' appended');
                createStramFile();
            });
            if (!files.length) {
                fileWriteStream.end("Done");
                console.log('copy Done');
                return;
            }

            fileWriteStream.on('data',function(chunk){
                console.log('copy data');
                return chunk+','
            });

            fileWriteStream.on('close',function(){
                console.log(fileNum);
                if (!fileNum) {
                    roMockJs()
                }
                --fileNum;
                console.log('copy over');
                //roMockJs();
            });

        }


    });