This is the second challenge of the Tuenti Contest 2015 solved in Node.js

node_challenge_2.js

'use strict';

var fs = require('fs');
var byline = require('byline');
var progress = require('progress');

var stream = byline(fs.createReadStream('challenge_2_input.txt', { encoding: 'utf8' }));
var total = 0;
var count = 0;

function semiPrime(n) {
    var aux = 0;
    for (var i = 2; i <= n; i++) {
        while (n % i == 0) {
            if (aux == 2) {
                return false;
            }
            aux++;
            n /= i;
        }
    }
    return aux == 2;
}

stream.on('data', function (line) {
    var output = 0;
    if (count == 0) {
        total = parseInt(line);
    }
    else {
        var len = parseInt(line.split(' ')[1]);
        var bar = new progress('calculating... ' + count + '/' + total + ' [:bar] :percent', {
            complete: '/',
            incomplete: ' ',
            width: 50,
            total: len
        });
        for (var i = parseInt(line.split(' ')[0]); i <= len; i++) {
            if (semiPrime(i)) {
                output++;
                bar.tick(i * 100 / len); // show progress
            }
        }
        fs.appendFileSync('challenge_2_output.txt', output + '\n');
    }
    count++;
});