Sum all primes

sumallprimes.js

/*
A prime number is defined as a number greater than one and having only two divisors,
one and itself. For example, 2 is a prime number because it's only divisible
by one and two.
*/


function getPrimes(max) {
    var sieve = [];
    var primes = [];
    var i;
    var j;

    for (i = 2; i <= max; i++) {
        if (!sieve[i]) {
            primes.push(i);
        }

        for (j = i << 1; j <= max;  j+= i) {
            sieve[j] = true;
        }
    }

    return primes;
}


function sumPrimes(num) {
    if (num < 2) return 'Please enter a number more than 2';

    return getPrimes(num).reduce(function(a, b) {
        return a + b;
    }, 0);
}

sumPrimes(977);