Javascript Number Integer Sum all prime numbers

// given a number, return the sum of all prime
// numbers less than or equal to the number itself

/**//w ww.  j av  a 2s . c o  m
  * @function sumAllPrimes
  * @param {number} num
  * @return {number}
  */

// Using the sieve method
function sumAllPrimes(num) {
  var allPrimes = Array(num+1).fill(true);
  var i, j;
  
  allPrimes[0] = false;
  allPrimes[1] = false;
  
  for (i = 2; i <= parseInt(Math.sqrt(num)); i++) {
    if (allPrimes[i]) {
      for (j = i*i; j <= num; j += i) {
        allPrimes[j] = false;
      }
    }
  }
  
  return allPrimes.reduce(function(acc, n, i) {
    return n ? (i + acc) : acc;
  }, 0);
}

console.log('sumAllPrimes(20) => ' + sumAllPrimes(20));