047.js

// Distinct primes factors

// https://projecteuler.net/problem=47

function primeFactors(n) {
    var factors = [];
    var d = 2, included = false;
    while (n > 1) {
        included = false;
        while (n % d === 0) {
            if (!included) factors.push(d);
            included = true;
            n = n/d;
        }
        d++;
        if (d*d > n && n > 1) {
            factors.push(n);
            break;
        }
    }
    return factors;
}

function consecutivePrimesStreak(length) {
    var len = 0, cnt = 1;
    while (len < length) {
        if (primeFactors(cnt).length === length) {
            len++;
        } else {
            len = 0;
        }
        cnt++;
    }
    return cnt - length;
}

console.log( consecutivePrimesStreak(4) );