function calcLineCount(filename, callback) {

    var fs = require('fs');

    var fileStream = fs.createReadStream(filename),

        lines = 0;

    fileStream.on('data', function (buf) {

        lines += buf.toString().match(/\n/g).length + 1;

    });

    fileStream.on('end', function () {

        callback(lines);

    });

}

calcLineCount('/Users/piaoger/Downloads/lc.js', function(lines) {

    console.log(lines);

});