node js callbacks - multiple callbacks - multiple versions

callbacks.js

//different version of same multiple callback function
//a b c in the order

//version 1 (not elegant way)
var fs = require('fs');
function asyncRead(callback){
    fs.readFile('sample.txt','utf8',function(err, data){
        if (err) raise ("no output file");
        var numberOfNewLines = data.split("\n");
        callback(numberOfNewLines);

            fs.readFile('sample1.txt','utf8',function(err, data){
            if (err) raise ("no output file");
            var numberOfNewLines = data.split("\n");
            callback(numberOfNewLines);

                fs.readFile('sample2.txt','utf8',function(err, data){
                if (err) raise ("no output file");
                var numberOfNewLines = data.split("\n");
                callback(numberOfNewLines);
                });
          });
    });    
}
asyncRead(function(array){console.log(array)});


//version 2
var fs = require('fs');
function asyncRead(callback){
    fs.readFile('sample.txt','utf8',cb);
}

function cb(err, data){
        if (err) raise ("no output file");
        var numberOfNewLines = data.split("\n");
        console.log(numberOfNewLines);
        fs.readFile('sample1.txt','utf8', cb1);
}

function cb1(err, data){
            if (err) raise ("no output file");
            var numberOfNewLines = data.split("\n");
            console.log(numberOfNewLines);

                fs.readFile('sample2.txt','utf8', cb2);
}
function cb2(err, data){
                if (err) raise ("no output file");
                var numberOfNewLines = data.split("\n");
                console.log(numberOfNewLines);
    };

asyncRead(function(array){console.log(array)});

//version 3 (preferred way)
var fs = require('fs');
function asyncRead(callback){
    fs.readFile('sample.txt','utf8',function(err, data){
        if (err) raise ("no output file");
        var numberOfNewLines = data.split("\n");
        callback(numberOfNewLines);
        helper(callback);
          });   
}
asyncRead(function(array){console.log(array)});

function helper(callback){
    fs.readFile('sample1.txt','utf8',function(err, data){
            if (err) raise ("no output file");
            var numberOfNewLines = data.split("\n");
            callback(numberOfNewLines);
             helper1(callback);
    });
}

function helper1(callback){
     fs.readFile('sample2.txt','utf8',function(err, data){
                if (err) raise ("no output file");
                var numberOfNewLines = data.split("\n");
                callback(numberOfNewLines);
                });
}