const readline = require('readline');
const fs = require('fs');

var file = 'path.to.file';
var linesCount = 0;
var rl = readline.createInterface({
    input: fs.createReadStream(file),
    output: process.stdout,
    terminal: false
});
rl.on('line', function (line) {
    linesCount++; // on each linebreak, add +1 to 'linesCount'
});
rl.on('close', function () {
    console.log(linesCount); // print the result when the 'close' event is called
});