Without 3rd party extensions! What you need are the fs, readline and stream module.

var fs = require('fs'),  
    readline = require('readline'),
    stream = require('stream');

var instream = fs.createReadStream('your/file'),  
    outstream = new stream,
    rl = readline.createInterface(instream, outstream);

rl.on('line', function(line) {  
  // process line here
});

rl.on('close', function() {  
  // do something on finish here
});

The solution comes from here