Read lines synchronously from file in Node.js

Question

I need to parse a file line by line in the following format with Node.js:

13 13 0 5 4 3 0 1 9 12 6 4 5 4 0 2 11 12 9 10 0 6 7 8 9 11 5 3 

It represents a graph. The first two lines are the number of edges and vertexes, followed by the edges.

I can accomplish the task with something like:

var fs = require('fs'); var readline = require('readline'); var read_stream = fs.createReadStream(filename); var rl = readline.createInterface({     input: read_stream }); var c = 0; var vertexes_number; var edges_number; var edges = []; rl.on('line', function(line){     if (c==0) {         vertexes_number = parseInt(line);     } else if (c==1) {         edges_number = parseInt(line);     } else {         edges.push(line.split(' '));     }     c++; }) .on('end', function(){     rl.close(); }) 

I understand this kind of things might not be what Node.js was thought for, but the cascaded if in the line callback does not really look elegant / readable to me.

Is there a way to read synchronously lines from a stream like in every other programming language?

I'm open to use plugins if there is not a built-in solution.

[EDIT]

Sorry, I should have made clearer that I would like to avoid loading the whole file in memory beforehand

Answer 1

My usual code part for such simple tasks:

var lines = require('fs').readFileSync(filename, 'utf-8')     .split('\n')     .filter(Boolean); 

lines is an array of strings without empty ones.

Answer 2

This project on github.com does exactly what I needed:

https://github.com/nacholibre/node-readlines

var readlines = require('n-readlines'); var liner = new readlines(filename);  var vertexes_number = parseInt(liner.next().toString('ascii')); var edges_number = parseInt(liner.next().toString('ascii')); var edges = []; var next; while (next = liner.next()) {     edges.push(next.toString('ascii').split(' ')); }